Hello. After pluging normal map to my shader, assign material node dramaticly slows down. I'read once some topic on this forum,(I cant find it right now) it it was about calculating tangents for normal maps, cuz that's what makes it so slow. Could someone elaborate on this? How to calculate them by my self to make this node fast?

I'm not sure why this would slow down the assign material node; the viewport slowness due to displacement/normal-map materials can be resolved by using PolyFrame to author tangentuattribute on the geometry.

If you can share a hip file, that would make it easier to help figure out what the issue is.