Litterally " in
den Arsch treten" means to kick someones butt. But it is used to
express that someone shuld hurry up, or you or anoher person want someone to hurry up.
Also "
mach ihm Dampf" is used as another phrase.
Example for "In den Arsch treten": "Wenn Du ihn siehst- tritt ihm in den Arsch" - if you see him, kick his
ass- meaning: make him hurry up, make him do this and that fast/ faster. Usually uesd if someone is already waiting for
something, someone who takes a long
time.