thank you for your question. If your salary is enough then they wont pay you, if they count you as a "Bedarfsgemeinschaft":
In the event that you live with your fiance for more than one year, in the same household, the existence of a "Bedarfsgemeinschaft" is automatically suspected.
If you do have seperate household/ Haushaltsgemeinschaft then you have to proof it.
Basically, however, the legislature cannot automatically assume the existence of such and if couples are unmarried, such in your case there is no obligation to cover the financial needs of eachother. Also, a period of one year is not representative. So if you do have separate households then you should appeal against the ALG 2 decision.
I hope I could help you, if you need further guidance please do not hesitate to use the community.