I found this beautiful dashboard online:
I already did a dashboard for mobile by myself and wanted to use this dashboard for my wall mounted tablet.
Problem is i have no clue how to get this dashboard from GitHub to HA.
Can anyone help my and explain how I can solve this?
Welcome to the forum, Fabian 
Unfortunately you can not just upload some dashboard to your Home Assistant instance but you have to build the interface by yourself.
Regarding VigoKrumins’ dasboard he provides you with all you need to mimic a dashboard like his but you have to build this for your particular HA installation by yourself using the provided skeleton/example files for it.
Just use your favorite search engine to learn how Lovelace works. A good start you might find HERE.