What is this "something with QR codes" method?
QR codes are the oddly looking black and white squares. What you do is open any Scanning app on your phone and scan the QR. It can be a link to a site, app or a copy of some string/password. There is nothing hard about it. Unless you don't use any smart phones or tablets?
The bitcoin is a bit difficult and the last time I played around with it was like 5 years ago. Maybe some things have changed since then and maybe different rooms have different steps involved so I'm not the best one to help you with BetOnline. The basic idea is:
You download a wallet.
It's an app that gives you a long string of random letters and numbers. That's your address which people can use to send you coins. Along with the long address, there is a QR code, which is the same as the address, just so it's easier for someone to scan it fast.
Then, you buy some bitcoin either online or from an IRL exchange (IDK about Germany, but a lot of exchange bureaus in Bulgaria buy and sell cryptos now)
There are so many different sites that provide that service... some of them provide you with both a wallet and buy and sell options. For those sites you need to register -> which deafeats the whole point of crypto's anonymity, and there is history of such sites losing their clients money, or simply stealing them.
It's much better to just pay cash to somebody and he just sends you the coin. The risky thing is, if you lose your phone or wipe it's memory, it's hard (but not impossible) to recover your funds. Of course there are a lot of back up stuff you can do to your wallet so you can be completely safe - like a "cold storage". This is basically a printout of something like a QR code (or maybe exactly, IDK) that restores your wallet. But if somebody has it - he can get access to your wallet.
Anyway, once you get those sweet desired one of a kind coins in your wallet, you send it to the room and I believe you should give them your bitcoin address so they know the money are coming from you.
Maybe check out if they have a tutorial on how to do all those stuff or watch a video on youtube, because I didn't say half the shit there is to know about those make-belief money 
