Catrin, are you planning to jog continuously for 60-90 minutes? IMO, that's a lot to bite off for a new runner. I had to build up for quite some time to even get to 60 minutes, and I don't think I'm atypical. Remember that you need to give your muscles, joints, ligaments, etc. time to adapt to running or risk an overuse injury--even if your form is otherwise good.