How to get prepaid internet in Germany?

I haven't been to Germany but I think the best place to ask is the hotel where he is going to staying at. Like you said most hotels provide wifi. I don't think hotels would ask for your user name and password. That is confidetial. The usual thing is that they would provide you with their password so you can use their wifi. Our house uses wifi and we have a password so our neighbors can't share our internet connection thus slowing ours. Also, my sister-in-law visited the Philippines and stayed in the hotel for a week so her guests can see her. The hotel provided her access to their wifi if she enters the password provided to her. Then she stayed with me for a month and used my wifi because I shared my password with her. There is also pre-paid access to internet connection wherein you buy credits for the time you are going to use the internet but you have to buy a gadget for it. In the Philippines, there is. I guess, in Germany they have something like it also. I hope that helps.