I imported a model but after i set the materials, these strange artifact appeared and the lighting seems wrong. I tried to recalculate the normals, disable/enable the autosmooth and other things but none of this worked. Someone have any ideas? EDIT: Enabling soft shadows make the artifacts less visible but the problem still persist, moreover I think that this is only diffusing and softening the shadows without removing the issue. blender version: 2.8 sorry for my bad english
I think what you need to enable is the "Soft Shadows" setting under the render settings tab in the shadows dropdown.
Below I have a model with a similar issue with the shadows looking really jagged and bad:
Then, I turn on 'Soft Shadows' (seen on the right), and it looks much better:
I am not 100% sure that this is your problem, but it might, be, so I hope it helps.