Need advice: sketchy landlord situation in Aachen (international student)

Hey everyone, I just moved to Germany from India, for my master’s at RWTH Aachen and ran into some trouble with housing. Couldn’t find a place on WG-Gesucht (only rejections), so I went through a contact my friend suggested (who moved to Germany with me). The landlord showed me videos of a shared flat and said I could visit first, then pay a €330 deposit, specifically in cash. I arrived on Oct 1, met him on Oct 2, saw the place — it looked okay, so I paid €330. He did not give me a receipt. He made me sign a document, but the rent and deposit amounts weren’t written in. He said once all 6 tenants sign, he’ll fill it out and then give me my copy.

Now it’s Oct 10, and only my friend and I have signed, so I can’t set up electricity, heating, or Wi-Fi contracts yet. I did my city registration using the paper he gave me, but I’m not sure if that’s okay legally. Here are my questions:

• Should I wait to pay the rent? Can he cause legal issues for me if I do not pay the rent as I am not able to live there yet?
• Is the contract valid if I don’t have a copy and the rent/deposit aren’t written in?
• Can I back out and get my deposit back somehow?
• is it legal that he expects the 6 tenants who don’t know each other to get contracts for heating and electricity?

Any help or pointers would mean a lot. I’m feeling a bit lost in a new country, and worried I might’ve been scammed. Many thanks for your help.