不打不相识(bù dǎ bù xiāngshí)from an exchange of blows, friendship grows

Explanation

“不打不相识”指经过交手，相互了解，能更好地结交、相处，成为朋友。
The phrase “不打不相识” means that after fighting, two people can better understand each other, get along with each other, and become good friends.
Words:

竞争对手jìnɡzhēnɡ duìshǒu:rival;
吵架chǎojià:argu.

Sentences

1. Jiǎ：Cóngqián wǒmen shì jìngzhēng duì shǒu, bù dǎ bù xiāngshí, duì ba？
甲：从前我们是竞争对手，不打不相识，对吧？
A: Once, we were rivals. It takes a fight to get to know each other, doesn’t it?

Yǐ：Duì, xiànzài wǒmen shì hǎo péngyou le.
乙：对，现在我们是好朋友了。
B: Yes, now we are good friends.

2. Jiǎ：Tāmen zhīqián yī jiànmiàn jiù chǎojià， xiànzài dào cháng zài yìqǐ wánr.
甲：他们之前一见面就吵架，现在倒常在一起玩儿。
A: Before, they would argue whenever they met, but now they like to hang out together.

Yǐ：Lǎohuà shuō, bù dǎ bù xiāngshí.
乙：老话说，不打不相识。
B: As the old saying, from an exchange of blows, friendship grows.