I am a unity developer and i am new to CryEngine i use version V(5). I recently found this on the marketplace: https://www.cryengine.com/marketplace/product/cryengine-gamesdk-sample-project
But is it possible to start working from this standard game? If so how can i edit the coding? for instance i want to edit the menu. How is this possible?
I can't find my answer on the docs and the CryEngine forum isn't working aswell.
Yes, in fact this project was the standard project for CryEngine until CE4. It is huge and some people say it is too messed up to start a full new game but for starters it is good to learn how the Engine is being used.
For coding you need visual studio and if you want to use c# (which I assume for a unity developer) you need some more stuff explained here.
In general I would recommend to click through the docs. They might not be as easy and detailed as you are used from Unity but for the most basic things they are sufficient. If you more documents and help, check out the forums and of course the original code.