Biology classes kinda get easier in the later years (at least they did for me), because although they start of with a lot of "don't worry about why this happens, just know that it happens", we got to the "this is why it happens", and it all starts to fall into place. There are some fundamental principles, so far as we actually know them, in biology, however it does seem to be taught in a broad-to-narrow direction that imo does a disservice to those wanting to really understand the mechanisms.