I submitted my short manuscript four months ago to a math journal. I sent a tracking email about the status of my paper and I was informed that the editor has a problem with finding appropriate reviewer and asked me to send him the name of potential reviewers. Can I withdraw my paper, because it seems to me it takes a very long time and I need it too much to publish soon.
You can withdraw your paper at any stage before it's published, although the longer you wait the more annoyed the journal might get (you are using up their reviewer resources after all). After it's published, you'll have to retract as opposed to withdraw it.