Answering the question after a long time its been asked. Hopefully it will help someone who is looking for it in 2022.
As per the documentation of creating and managing projects in google cloud. its a simple process.
Search for IAM & Admin in global search.
Once we click on IAM & Admin we will land up in a page as follows.
Go to settings page from the left menu
It will take us to the currently selected project's settings page. On top there is a shutdown button. Press that for deleting the project.
Please note as per the official documentation,
This method immediately marks a project to be deleted. A notification email will be sent to the user who initiated the delete operation and the Technical category contacts that are listed in Essential Contacts. If there's no contact in the Technical category, the fallback contact will not be notified. A project that is marked for deletion is not usable. If the project has a billing account associated with it, that association is broken, and isn't reinstated if the project delete operation is canceled. After 30 days, the project is fully deleted.
Once we press the shutdown button, GCP will show a popup as shown below.
As a confirmation GCP is asking for project id to be manually entered in the popup. Enter the project id with caution and press shutdown in the popup.
It will show the success message as show below.
That's it. Hope it will help someone.