Hi, so my problem is that I made eyes of a model as separate object and now I can’t find a way to switch back to editing main object I can only edit eyes.
I tried to search how to do it in google, youtube and this forum, but nothing came up, mainly because I don’t really know how to properly word it.
Thanks in advance. 
It would help if you posted a screenshot with the Subtool palette open.
If I were to guess, I would say that you didn’t Append a sphere to use for the eyes but just drew it on top of the model. If that’s the case, then the model would have been dropped to the canvas when you drew the sphere, making it 2.5D and no longer editable in 3D mode. Only the last thing you drew on the canvas would be editable.