Hello

As I see now, there is a time difference of 2 hours between
my PC and the server time of this forum.

For the forum "your PC" is inexistent. The output of the forum will be generated on the webserver if someone (i.e. you) makes a request for a page of the forum. If you visit a website in Indonesia and you are located in netherlands (what your name sounds to me) you will not expect to see your local time at the page (if there is a shown time).

I don't know every single detail of Alex's implementation, but there at least two settings. The first setting belongs the admin or, to be specifically, the forum server. There you —as the admin— have to set the local time zone of the server. The second setting belongs the registered user of the forum. It is his home time zone. Over the loop way of GMT/UTC you as an registered user sees the posting times in your home time zone.

I don't know where this server is located.....

Errr, ask your hoster!?

Tschö, Auge