wizisi2k: step 1: make a ticket that your account has been compromised (add ALL the information they ask for in the 1st post)
step 2: contact local consumer affairs office (or whoever handles consumer complaints for Steam in Germany)
step 3: watch as they respond
It sadly sounds like you had the EXACT same thing happen to you that I did-someone hacked your account. What I listed above worked for me except I contacted WA consumer affairs since I am in the US. If you contact them, you won't have to wait 3+ weeks for a response. Once you get your account back, you cannot trade for 15 days.
well before step 1 , if more people cared a bit more about securiy , there won't be so many account compromised.... nothing is 100% full proof , but sometimes .......just the password ...