i wantd to make a "line" around the model. The only solution i found is to select the edges for the line and press "s" to put them more into the model. But then i need to select every single edge left and right on that "line" to put them more together to get that "deep" effect. Is there an easier solution to do that? It does not only take alot of time to select and move every edge the bigger problem is that the edges arent all at the same spot to have a smove line.
If your edge loop is clean (i.e. you can go around your "ring" by walking only along quadrilateral faces) you can use loop cuts:
CtrlR, find the correct area (pink line), LMB to accept the region, Enter to accept the position
(this creates the line that will be then "buried")
Same as before, to the right and to the left of the middle line. This time, though, slide the "line preview" to make it closer to the centre line before accepting (Enter)
(Alternatively you can AltRMB select the middle line then CtrlShiftR to make two lines around it)
deselect all (A), then AltRMB to select the middle line, and finally S to scale it inwards
P.S. instead of making 3 cuts and shrinking the middle one, you can also make 2 cuts and shrink (E then AltS) the faces between them. I personally suggest this method.