you would be better off contacting a dealer, um, i'm assuming you are in germany so i woldnt know where to start over there, contact your nearest specialist comic shop and they should be able to point you in the right direction though.
a quick google gives me
http://www.comicspriceguide.com/ which at least seems to know what its doing, although i must admit its been a long long time since i looked at prices so i don't know how accurate it is.
another thing though, as with everything, condition is PARAMOUNT, so i hope you havent just been keeping them all stuffed in boxes, but have taken loving care of each and every one
good luck
hope some of them are worth something for you mate