Translation:Please do not play tennis here.
This is an operating room. Why would you even want to play tennis here? Please leave.
Maybe they are playing tennis on the place (here) what is not tennis court. :D
They are playing tennis somewhere that is not a tennis court.
To say "please don't do X" in Japanese, you use the negative -te form of the verb + kudasai. The negative -te form of やる (yaru, no kanji necessary) is やらないで (yaranaide).
You would use やらなくて (yaranakute) if you were asking permission to not do something.
Yaranakute mo ii desu ka?
Is it okay if I don't do it?
Can we omit "please"? "Do not play tennis here" was marked wrong.
ここでテニスをやらないで (koko de tenisu o yaranaide)
Don't play tennis here.
ここでテニスをやらないでください (koko de tenisu o yaranaide kudasai)
Please don't play tennis here.
The word "early" is not in the Japanese sentence.
ここで (koko de) - here
テニスを (tenisu o) - tennis
やらないで (yaranaide) - do not play
ください (kudasai) - please