It;s idiomatic to English and does not really mean anything in German, but if you wanted to translate it, you would have to say Steck eine Gabel (in mich) rein. Ich glaube, ich bin gar. (like: well done - as in cooking) But as I said, it does not translate well into German. You should say: Mir reicht's! Oder: Ich habe genug!

Almost. Steche eine Gabel in mich, ich bin fertig.

danke everyones for antworts! schoenen guten what ever time of day it is now in euren Länder.