Walls were smooth at first, but after painting, there are grooves and marks

It remains only that it was not smooth.

Once again for you: If it is rougher after painting than before, it does not matter how smooth it was before. It has worsened! Understood now?

I used primer from B1 and a brush to apply it.

Did you have a continuous film after applying the deep primer? If yes, the gypsum plaster was either not absorbent enough or applied too thickly, the grooves then formed due to binder accumulation. But this should also be stated in the processing instructions. Probably only sanding and repainting will help, of course without any further priming.

Mr. Baumeister is right, and I have beautiful walls. Thats it.