The main thing to understand about the Octatrack is there are a myriad of uses cases, you could for example use a project for each song - with no requirement to use all the parts, slots, patterns banks etc. Or you could have an entire album or live set in a project, this takes a bit more planning, and a greater understanding of slots, parts and banks. In short there isn’t a way it is “meant” to be used, there are many ways you can choose though.
At first, as you have discovered it can seem a bit counter intuitive and obtuse, but eventually you realise that its flexibility is its strength, the best thing that I can suggest it to spend some time actively not trying to work on anything other than learning how everything works, be prepared to inadvertently lose record buffers, mess up your parts and find the other (many) limitations, remembering that you can save if you get something you like.
Read the manual, merlins guide (search forum for it) watch videos, and consider joining in here: