Missing catalog data after upgrading PC

[CGT-Earty]

Hello,

I have a problem with a catalog. I build a new PC and changed everything except the hard drives.
When starting the new PC everything was fine but Lightroom was empty. So I searched for the catalog in the HD tried to start it but it said I have to update it to V12 which I did without concern.
The update didn't went through and I had to restart the System. After trying again a new catalog file was there it is 1,4 GB big and I thought nice the catalog should be back. But it was't it's just showing the list of the folders but not one picture. I tried the search bar and everything I could find to sync again but nothing worked.  I searched for other lrcat files found some but non of them included my pictures. I tried to start the old catalog file with an older version (V11) also didn't want to start without updating it.  I found some articles that said when you update your catalog it could be damaged and a lot of pictures could be missing. (https://helpx.adobe.com/lightroom-classic/kb/recover-catalog-images-resetting-lightroom.html)
I also called the support of Adobe but they couldn't help me either.  

So what can I do to get my catalog back to work again?

Thanks for helping.

Enclosed some screenshots of folders Lightroom etc. 

[dj_paige]

Most likely you have updated the wrong catalog file. Use your operating system's search feature to find all files whose name ends with .LRCAT, and upgrade each until you find the one that has everything you expect.

[CGT-Earty]

Upadated every lrcat file on the system but non off them had all pictures. Iam pretty sure that the "Alte Bilder" lrcat was the right one but I tried to update again and it was still empty. 😕

[dj_paige]

Open a recent backup from the old computer which was made during a time when LrC was working properly.