Thanks for thinking with me guyz, I realy appreciate that!

And yes, back in december 18th 2013 I think I used the blockchain.info wallet. Generated this adress: 1MAUuNVNQgc4s5Cp15Xz9R7wD5DamwG5mL and sent 1 btc to that.
You can still see it rock-solid in his place, never moved since then.

Now I found a screenshot of a 17 words seed. That's made the same day, later that day.

The Support team of Blockchain.com uses their favorite word to reply to my mails. That is: "unable".

I tried btcrecover with Python.
I tried old versions of Electrum (did not start)
I tried a 4.5.8. I only could import the 17 word seed as bip39. But I know already some words are not compatible with that list.

I hope somebody can give me the $ 100.00+ advice! :-)