I am not a real musician, but nevertheless:

Have a look at the discussion board at "mandolincafe.com" - you can get a lot of technical advice there. Also links to websites of various mandolin-players so you can get an idea what style you would like to learn.

For easy tunes and tab I found the sites "jaybuckey.com" and "nigelgatherer.com" very helpful.

Also you might look what local mando-players are doing. Since you live in the cologne area, you might check a group called Wayfairing Strangers, one of them (his name is Martin Ahrndt, I think) plays mandolin.

Happy Picking!
Ernest