When I start the game it's not going on full-screen. Now I can't do anything because I can't see some buttons. Can someone help me to play it on full-screen?

Hello!

When you open the launcher, before you press Start Game, press Options. From that, go to Video. From there, you can choose the resolution you want, and whether or not it is full screen or windowed.

I hope that helps you! ^_^