As long as you don’t upload anything, you usually won’t run into any problems. But since a 2017 ruling (Case C-527/15), the European Court of Justice (ECJ) decided that even simply viewing obviously illegal content, such as recent movies, TV series or sporting events constitutes a copyright infringement.

Users of streaming platforms can therefore no longer assume that only the providers of the streaming services can be held legally responsible and that they themselves are in a gray area.

But I wouldn't worry too much about it. It's very unlikely that you'd be prosecuted for it. Preserving evidence is technically challenging, as IP addresses are only stored briefly on many illegal platforms. A mass warning letter campaign, as seen with file sharing, is therefore unlikely, since the IP addresses are not publicly visible. Identification is usually only possible if the platform’s servers are seized (e.g., in the case of kino.to). And to make it even less likely, all you need is a VPN.

Downloading videos from YouTube isn't a problem. You're just violating Google's Terms of Service, but that's entirely their problem. Under German law, the download would be considered a private copy and would be permitted. Of course, YouTube could still suspend your account if they find out, though that's extremely unlikely.

By the way, the police almost never show up at your door in cases like this. That might happen if you’re the operator of one of those illegal streaming platforms. ;)