I used Smooth on 1 picture - model did not smooth where polygons bended in a sharp angle.
Second picture - there is a polygon did bend (it is dark)
I can't help preventing this happen. Is there a way to avoid that still using the Retopoflow ?
Looks like the problem wasn't exactly in Retopoflow, it is my quads were being created not planar but somehow triangulated. I found out that I can use the Mesh - Clean Up - Make Planar Faces to flatten my poligons.