change your $sql to this:
$sql3 = "INSERT INTO `".$prefix."".$titlu."`(numecap, contentcap) VALUES ('$numecap[$i]', '$contentcap[$i]')";
because that way, you create a new row, insert only one value. create a new row, insert next value. And so on.
Your for loop should look like this:
for($i=0;$i<$count_name ;$i++){
$_numecap = mysqli_escape_string($con,$numecap[$i]);
$_contentcap = mysqli_escape_string($con, $contentcap[$i]);
$sql3 = "INSERT INTO `".$prefix."".$titlu."`(numecap, contentcap) VALUES ('$_numecap', '$_contentcap')";
mysqli_query($c, $sql3);
}