Try something like this. My suggestion is to stay away from "magical" margin and padding numbers such as 255 dp and such. Try centering elements
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:background="@drawable/mediib"
android:orientation="vertical"
android:weightSum="2" >
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:orientation="horizontal"
android:weightSum="2" >
<LinearLayout
android:id="@+id/linearLayout1"
android:layout_width="160dp"
android:layout_height="200dp"
android:layout_marginLeft="37dp"
android:layout_marginTop="255dp"
android:layout_weight="1"
android:orientation="vertical" >
<EditText
android:id="@+id/editText1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/nota2"
android:gravity="center"
android:hint="@string/nota"
android:inputType="number"
android:textColorHint="@color/white" />
<Button
android:id="@+id/button2"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/bb" />
<Button
android:id="@+id/button1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/bbc" />
<TextView
android:id="@+id/textView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:text="TextView"
android:textColor="@color/white"
android:textSize="25sp" />
</LinearLayout>
<LinearLayout
android:id="@+id/linearLayout3"
android:layout_width="160dp"
android:layout_height="200dp"
android:layout_marginRight="33dp"
android:layout_weight="1"
android:orientation="vertical" >
<EditText
android:id="@+id/EditText02"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/nota2"
android:gravity="center"
android:hint="@string/nota"
android:inputType="number"
android:textColorHint="@color/white" >
<requestFocus />
</EditText>
<EditText
android:id="@+id/EditText01"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/nota2"
android:gravity="center"
android:hint="@string/teze"
android:inputType="number"
android:textColorHint="@color/white" />
<Button
android:id="@+id/Button02"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/bb" />
<Button
android:id="@+id/Button01"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/bbc" />
<TextView
android:id="@+id/TextView01"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:text="TextView"
android:textColor="@color/white"
android:textSize="25sp" />
</LinearLayout>
</LinearLayout>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:orientation="horizontal"
android:weightSum="2" >
<LinearLayout
android:id="@+id/linearLayout4"
android:layout_width="160dp"
android:layout_height="200dp"
android:layout_marginBottom="45dp"
android:layout_weight="1"
android:orientation="vertical" >
<EditText
android:id="@+id/EditText03"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/nota2"
android:gravity="center"
android:hint="@string/nota"
android:inputType="number"
android:textColorHint="@color/white" />
<Button
android:id="@+id/Button06"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/bb" />
<Button
android:id="@+id/Button05"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/bbc" />
<TextView
android:id="@+id/TextView03"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:text="TextView"
android:textColor="@color/white"
android:textSize="25sp" />
</LinearLayout>
<LinearLayout
android:id="@+id/linearLayout2"
android:layout_width="160dp"
android:layout_height="200dp"
android:layout_weight="1"
android:orientation="vertical" >
<EditText
android:id="@+id/EditText04"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/nota2"
android:gravity="center"
android:hint="@string/nota"
android:inputType="number"
android:textColorHint="@color/white" />
<Button
android:id="@+id/Button04"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/bb" />
<Button
android:id="@+id/Button03"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:background="@drawable/bbc" />
<TextView
android:id="@+id/TextView02"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:gravity="center"
android:text="TextView"
android:textColor="@color/white"
android:textSize="25sp" />
</LinearLayout>
</LinearLayout>
</LinearLayout>
EDIT: I eddited it quite a bit removed the pictures and strings so I can see it in my eclipse you might want to add those back. I got a very similar look to what you are trying to achieve in the picture. Is this what you are trying to achieve?
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent"
android:orientation="vertical"
android:weightSum="2" >
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:orientation="horizontal"
android:weightSum="2" >
<LinearLayout
android:id="@+id/linearLayout1"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:gravity="center"
android:orientation="vertical" >
<EditText
android:id="@+id/editText1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="number"
android:text="asd" />
<Button
android:id="@+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="asd" />
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="asd" />
<TextView
android:id="@+id/textView1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="TextView"
android:textSize="25sp" />
</LinearLayout>
<LinearLayout
android:id="@+id/linearLayout3"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:gravity="center"
android:orientation="vertical" >
<EditText
android:id="@+id/EditText02"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:inputType="number"
android:text="asd" >
</EditText>
<EditText
android:id="@+id/EditText01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:inputType="number"
android:text="asd" />
<Button
android:id="@+id/Button02"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="asd" />
<Button
android:id="@+id/Button01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="asd" />
<TextView
android:id="@+id/TextView01"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:text="TextView"
android:textSize="25sp" />
</LinearLayout>
</LinearLayout>
<LinearLayout
android:layout_width="fill_parent"
android:layout_height="wrap_content"
android:layout_weight="1"
android:orientation="horizontal"
android:weightSum="2" >
<LinearLayout
android:id="@+id/linearLayout4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:gravity="center"
android:orientation="vertical" >
<EditText
android:id="@+id/EditText03"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:inputType="number"
android:text="asd" />
<Button
android:id="@+id/Button06"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="asd" />
<Button
android:id="@+id/Button05"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="asd" />
<TextView
android:id="@+id/TextView03"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:text="TextView"
android:textSize="25sp" />
</LinearLayout>
<LinearLayout
android:id="@+id/linearLayout2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_weight="1"
android:gravity="center"
android:orientation="vertical" >
<EditText
android:id="@+id/EditText04"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:inputType="number"
android:text="asd" />
<Button
android:id="@+id/Button04"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="asd" />
<Button
android:id="@+id/Button03"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="asd" />
<TextView
android:id="@+id/TextView02"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:gravity="center"
android:text="TextView"
android:textSize="25sp" />
</LinearLayout>
</LinearLayout>
</LinearLayout>