Edit solved I have a cold so forgive me forgot to have the group button on
I want to save area that i grouped visiblle in dynamesh. is it possible to save it once i insert a object and cntrl drag twice?
Probably not. Polygroups are based on the topology/vertices, and dynamesh essentially changes that everytime it remeshes. You could try marking the polygroups by polypaint, dynameshing a clone of the tool, and then try projecting the colors back and creating polygroups from the polypaint.