I suspect that you could get a quicker answer if you asked a question in English. You don't know English? It doesn't matter. You can use Google Translator:
https://translate.google.comTo encourage you (or rather "*****" you) to use it, I will answer in English:
Q: Wie bewerte ich Models?
A: You can rate the card via the iStripper application. Open details page of the specific card and click the button next to the rating (see screenshot).
Q: Kann ich nur gekaufte Models bewerten?
A: Yes, you can only rate cards that you have bought and have in your collection.
Q: Geht das über die Mobile Seite?
A: No, card rating is not possible via the website. You can do it only using the desktop application.