Photoshop has some 'reasonable' learning files in its own program program folder. Some are advanced techniques of using the program. Check the tutorials there.
... oh .. just checked .. the more recent version Photoshop doesn't seem to have such entailed tutorials. They do link from URL page however so that's probably how they do it now I guess.

The Adobe site used to have pages for both tutorials & examples of work. I haven't checked in a long time as to whether they still exist.

Personally I was self taught, but later studied Photoshop at university (was exempted for early part) as a part of a multimedia graphics course. I spent much of my time helping others. lol