As an asylum seeker you are not allowed to leave Germany for the duration of your asylum procedure. If you get a residence permit for Germany you will also receive a blue passport that allows you to travel visa-free to a lot of European countries including Poland.
So, as a refugee (not an asylum seeker) you can marry in Poland if you fulfil all the requirements. It can be that you need a special visa to enter Poland if you want to marry there. I don’t know about the exact ruling, so probably it’s best that you get in touch with Polish authorities once you are allowed to travel.