Thank you Mads, I checked your tricks and most of them works great!:) Thank you for Bump2Normal and NormalBlend shaders, now I can combine Bump and Normal map, it works even with arnold standard material, as you said.
But I have no idea why NormalBump map doesn't work anymore. There was 2 slots, one for Normal map and second for additional Bump map, I could increase or decrease strength of every map. Now I can't because Arnold doesn't see additional Bump map, only Normal map. Maybe I should put some map in the Additional Bump slot (for bump), and then import final Bump texture?
I tried BitmapLookup map for UDIMs as well, and it works perfect! Now working with UDIMs is sooo simple, Thaaank you Mads!!! 😄
And last thing - combinig the displacement maps. I used Add(Vector) map for combining 2 displacement maps (as you showed me), and it's combining them. I can increase and decrease strength of every displacement map, but there is one thing which is not working good - Add(Vecor) map is distorting my displacement maps. When I use my disp map straight to Arnold Properties modiffier, it looks ok. But if I put it in Add(Vector) map and then in Arnold Properties modiffier, then my disp is distorted - I think it looks like inverted? And what is more, whole object is shifted a little bit. I attached a screenshot.