I want to merge two projects but I can't have two activities with the same name 'main'.
I couldn't change the name of the main activity into another name.. I searched the forum but
there was 0 hits.
Any help appreciated.
I assume by merging you mean copying each module from one project to another. The you need to decide which of the two main modules really is the new main module, and copy the second one to a module with a different name.
You can use import existing modules for those that have different names, for the main module open the two projects at once, create a new module in the new project named whatever you decide and use copy and paste from the old main in the original project to the new module in the new project.