“I’ve had enough of your constant arguing! If you two can’t get along, go fight somewhere else.”
When you’ve had enough of something, you can’t take it anymore. You’re sick and tired of it. Of course, you can also say, “I’ve had enough,” to indicate that you don’t want any more food when offered seconds.
「もうあなたたちの口げんかはたくさんだ!仲良くできないなら別のところでやりなさい。」
何かが「もうたくさん」なときは、もう我慢の限界だったり、もう耐えられません。もちろん、お代わりを断るときにも使えます。