After quite some time, I've decided to come back to IRC.Hi Leito, and welcome back to Undernet.
But to my surprise almost every channel is set to +R.
Question: how can I chat with my friends on IRC when I CANT register a username and the channel is set to +R?
I believe you mean the channels you want to join are set +r (lower-case.) +R (upper-case) simply means the channel is registered.
+r means only people logged in to X can join. And since no one has been able to register a username since last November or so, you cannot get in simply by registering a username and logging in. The only way to bypass that is ask for an invitation from an op in the channel. If you don't know any to message, sometimes ops will show up in a /who #channelname inquiry.