Hello @Mirko!
It looks like you have some sort of overlapping mesh in your subtool. Since this appears to be in a “merged” tool, I should mention that “merging” subtools in the subtool palette does not fuse meshes together. It only regroups the meshes into a single subtool. A single subtool may contain multiple meshes.
Dynamesh will fuse meshes together. You might be able to clean up whatever is going on by dynameshing that subtool, although at this stage of your work and experience it may be easier just to start over.
To remesh with more resolution with dynamesh, you must increase the resolution slider in the dynamesh menu. This will let you sculpt finer detail, but be aware that dynamesh works best at the low-medium/medium-high detail range. Once you get your basic form established and there is a reduced need for frequent dynameshing, you may wish to subdivide your mesh into multiple subdivision levels to sculpt ultra-fine detail.
Sculptris Pro mode is also very useful to be able to add and remove geometry in real time with certain brushes, so you can sculpt hi-rez detail even on a low poly mesh.
If you’re new to Zbrush and digital sculpting in general, you should start at the ground floor and learn the fundamentals of the program, or else everything else you try to do will be more difficult. The Pixologic Classroom is a good place to start.
Good Luck!
