You can’t work on the same project file, obviously, sounds like you need to just set up rules for who is working on what.
Import from FCP into AE. Copy the project file so now you both have the same comp(s).
You don’t say if there are multiple comps or one long comp, or what, but clearly you work on some bits and your friend works on other bits. If you’re networked together you can both use the same source media.
— Wes Plate
Automatic Duck