Can someone link me a video please, i can't find anything.
I have dedicated server, i've installed xamp put everything in htdocs/web/ and updated composer but still not working. 

Documentation for the web app installation can be found here.

As mentioned there, subdirectory installations (e.g. /web/) aren't supported (unless you're mapping a (sub)domain root to them).

Dependencies are preinstalled, using Composer isn't required.