Hi bence8810, welcome to APUG!
Forte Bromofort BN was my favourite paper, NB0 was single weight, normal gradation, BN4 was double weight, glossy. It was fairly fast paper, maybe full grade more contrasty than "normal" EFKE Emaks #2. Generally speaking, Forte Bromofort was long lasting paper. I printed on +20 years old 50x60cm somebody give me back in the day, with no problem. From what you said about being in the "block", it doesn't sound good. Being single weight you have good chance in damaging emulsion. Try slowly in the dark some card tricks??? Never had a chance to experience that phenomena. Generally single weight Forte in 18x24cm size after opening was always well curved on all 4 corners, looking more like bowl, but in easel, under weight it was flat.
Did it come packaged with red wrapper after black one in the box?
Good luck!
PS maybe it's time to finally use all my remaining Forte Bromofort BSP0 and BH0 I have left from my last visit to Forte factory shop in downtown Budapest in 1993?