Finally I had enough courage to cut them in two.
W H A T ? ? ?
Yes! I cut them in two. Both socks. Then I picked up the trash...
...and worked over a tray to avoid huge mess.
I picked up the stitches on knitting needles...
...and bind off the knitting.
Then I crocheted the decoration edge. I used the yarn from the leg parts of the original long socks.
And yes indeed they turn out pretty useful socks which were not too thin anymore.
Often you see this to be done opposite. Meaning that the leg parts of the socks are still just fine but the heels and soles have holes. In that case you cut off the foot part and knit new ones. But in this time I needed to shorten the sock to make them still to fit.