If I remember correctly, your first asylum application and the appeal got rejected, right? That means that you can't travel to Poland anyway. But if your fiancé is allowed to come to Germany you can try to marry here.
As a fully acknowledged refugee with valid travel documents (blue passport) you could travel to Poland and get in touch with the Civil Registry Office. You have to submit a number of documents: a proof of identity (e.g. a valid passport), a certificate of birth (translated into Polish), a certificate of no impediment and (if necessary) certificates that prove that previous marriages have been divorced etc. The Registry Office will guide you through the procedure from there on.
For extensive information about marriage in Poland please check out this website: