YOU SAID:
your mom is a baka doing parkour on her knees
INTO JAPANESE
あなたのお母さんは膝の上でパルクールをしているバカです
BACK INTO ENGLISH
Your mom is an idiot doing parkour on her lap
INTO JAPANESE
あなたのお母さんは彼女の膝の上でパルクールをしているばかです
BACK INTO ENGLISH
Your mom is an idiot doing parkour on her lap
That didn't even make that much sense in English.