Could not extend oxid core in vendorfolder

I try to extend the oxcategory-model with an own modul (oxid 4.7.10). Everythings works very well, if i run the modul directly in the /modules/ folder. But if i copy this folder into my venderfolder (/modules/myvendor/) it does not work any more. All the other modules in the same vendorfolder still work.

Before i copied the modul, i deactivate it. After i copied the modul i was editing the metadata file to change the path to my oxcategory-model. My vendormetadata.php is still empty.

What is wrong with the vendorfolder?