OMG - I got my data back (:

after putting hours after hours and day after day into trying around
also trying to get a new SSD, at least as big as the "old" (while they are not available for me atm),

and despairing

I've now tried again - on another linux laptop - and managed to make my SSD work again in just a few seconds..

I haven't tried that before, cuz I was advised to first make a complete dd copy image of the drive and experiment with that copy instead of the drive itself - to avoid writing on it and destroying the drive itself
if something goes really bad one was only destroying the copy image instead of the drive itself

but I now just tried on it directly

and as said: it got it working again in only a few seconds :)))

oh man, I'm so relieved

will still try to get another drive for a backup ^^ and probably never again plug anything into windows ;)