It was a surprise to me to say the least!
I do completely understand your predicament though. Do you know anyone in Germany that could check it over for you? Ask the seller to post dated pics to you personalised so you can get proof it actually exists? Ask for feedback references from other sites, Facebook possibly, other bass forums etc?
I did complete one transaction using google translate with another German seller who wouldn’t ship internationally - we arranged to send the bass to a German friend, they checked it over and sent it on to me.