Thank you Evo for the warning. I've had penpals to improve my language skills and most of them have turned out to be very nice people. But unfortunately they at best didn't mind talking about mathematics.
Ivan92, I'm not really looking for dating or anything similar. And I have an age requirement only because I like to discuss ideas with someone who knows roughly as much as I know. It would be great to work on interesting problems and read books together. If someone is much younger or older than me, then they usually know much less or more than I. Sure I can get my questions answered this way, but that's not what I'm looking for either. I hope this clarifies my point.
micromass, I'm afraid you know too much for my purposes, but I hope we can be friends here in PF at least.
And wisvuze, I'll PM you to see if we have anything to talk about.
Thank you all for your posts.