Problem with using/viewing gallery.

Hey everyone! At the begining I've to say that my english isnt good and ive just started my journey with Contao. Btw. this system is awsome! Ive decided to use it in practise. Ive almost created site, its hunting club website, but ive a problem with gallery. I need hierarhy like this:

Code:

Categorie 1 -> Categorie 1a -> Photos -> Categorie 1b -> Photos Categorie 2 -> Categorie 2a -> Photos -> Categorie 2b -> Potos etc.

The problem is that I dont get how does gallery extension works, I was trying to find any guide or something. Also I want members to upload a images. Ive to end this website today or tomorrow morning and im in hole :/ Can You help me with this? Rly sorry for my english.