I couldn't find the info I wanted about this, so I'm sorry if I shouldn't ask it here. How long does it take for someone to lock a topic more or less? Do I need to do anything else besides changing topic name to "please lock" or similar?

nothing more is needed. Because it is dependent on whether or not the MM is around and active, and because it is a service and not a requirement,it could take as long as two to three days. The MMs are human and they do get time off/fail to see etc. If you're in a subforum that doesn't have an MM then you might need to file a Ticket in Help if you're in a hurry, but someone should come along and lock it eventually even if you don't.

Ahh I see, okay thank you. So if my topic is in the 4th or 5th page should I just file a ticket? Because I wanted to open a new topic in the art market but I'm only allowed one open topic at a time. But I don't wanna be a bother if it's unnecessary. edit: topic is locked, resolved ^^