You don't really need to be sure of whether it's a scam or not. Lots of time it's enough to just weigh down the risks and see if that is something you can take in. You might find more reviews in german speaking communities but I doubt it's gonna be up to reputable level. If you can, you should stick to those reputable websites.
Maybe I'm nitpicking but I noticed their twitter has turned into a personal account rather than a business type. A great example is them retweeting this:
🔥 Announcement 🔥
We are looking for people to test our game👀
Tester will get 5 free Nfts!
How to be a tester:
✅Follow us
✅Like and retweet
We will pick 3 people!
$Htr #NFTs #P2E #Nft
Their last tweet about their platform was on 2020. Coincidentally, their promotional activities in bitcointalk, coinforum.de, facebook, medium all stopped sometime in the same year with their domain
set to expire in a few months. Because of this, the service appears unprofessional and neglected. Couple that with little to no trustworthy reviews and I'd be marching away from it.