@Eva2412 ,
I would try to contact your host, send him a message an let him know, that you really want to book but you currently are have problems with your verification to get this done in system and you are about to sort this out with the support tommorow. Your host should be able to send you a host offer, where the discount is already included, and this host offer then will be valid for another 24 hours (and if needed the host can renew this after it is expired)
Ask your host about the discount, may be he knows the reason or may be he is not aware of the changed pricing.
Übrigens, Du bist hier im deutschsprachigen Community Center. Ich bin mir nicht sicher, ob Du Deutsch sprichst oder lieber auf Englisch kommunizierst.