Why do you keep doing it when you know he/she doesn't like it?
Why do you keep repeating the same behaviour even though you know he/she doesn't like it?
「相手が嫌がると分かってることをなんで何回もするの」＝ Why do you keep doing it when you know he/she doesn't like it? / Why do you keep repeating the same behaviour even though you know he/she doesn't like it?
ボキャブラリー
why ＝ なぜ、なんで
keep doing ～ ＝ ～を繰り返す、～をやり続ける
he/she doesn't like it ＝ 相手（彼・彼女）が嫌がる
even though you know ＝ あなたが分かっているのに
イギリス 
