Simplify part of mesh?

Suppose I had a high ply mesh that needs to be so for some curves in places or details. But what if I want to simplify part of a mesh? Is there such a tool?
I hope you get what I mean…

Try the decimate modifier maybe…

Not an option, way too ugly results, at for part of a mesh… Anyway I’ll try to find another way.

Sorry Antoni this is retopology and not automated in Blender at this time. Manual process. I understand 3Dcoat is currently the leader in this field if you want to shell out the shek.