In Version 3 (wpshopgermany) the images where saved here ".../uploads/wpsg/wpsg_produktbilder/$Produkt-ID", but in Version 4 (wpshopgermany) the shop is saving the images in the Wordpress library. The Wordpress library creates for each month (every year) a new folder... you can find the images that were uploaded in Mai 2020 here "/wp-content/uploads/2020/05/".
The Shop is loading all images to the wordpress library with the update from 3 to 4.
I think your main problem is that your update from 3 to 4 failed?
Greetings Karl