The cycle modus is very nice for recording vocals. You have all takes under each other, so you can pick the best parts to make your track. Is this way of working also possible with imported vocal tracks ? I mean ... tracks that you receive from someone and edit them like tracks recorded in cycle modus ?

Sure. Import the various vocal files/takes as shown, select them, and right-click on one; then choose "Pack Take Folder" (or use the associated key command Cntl-Opt-Comm-F). The files will be packed into a Take Folder, same as if you'd recorded them that way in Logic. You can then utilize all the normal Take Folder editing capabilities.