Problem updating projects to 4.18

I haven’t used Unreal Engine for a while, so I decided to update some of my old projects to the newest version (4.18 in this case). I tried to mannualy rebuild my projects from the source like I usually do, but for some reason, my code is marked with errors that I am sure were not there when I last opened the project. Classes like “InputComponent” and “PhysicsHandle” are now undefined and I do not know why.

Any help with this would be appreciated.