So I am watching a "How to sculpt stylized character head" tutorial (https://www.youtube.com/watch?v=usbupwLRENE). I joined neck and upper body together with ctrl + j.
After that, the neck is green in sculpt mode and the sculpting is odd, but why? To try out anoter way I used the Bool Tool Add-On´s Union function. Than a box appears, indicating that the meshes didn´t realy merge.
When I merged meshes with the Bool Tool before the borders merged very fluently when sculpted on. That isn´t the case here.