When I open AE I have numerous errors notifications?
You are not using English version of the software. Because of that, some of expressions used inside the project has got broken connections.
Easy fix: You need to create an empty txt document “ae_force_english.txt” put this document into user/document. When you start AE it will run in English.
When I open project I dont see Element 3D files?
You must relink the element 3D files, so that AE can properly read their locations.
Here is a short tutorial about that https://www.youtube.com/watch?v=yBxadX8qpnE