"不善交友" 用英语可以说作 "not good at making friends" 。
"Making friends" 指的是交朋友的行为。 "Not good at" 意思是不擅长。
例如:
He is not good at making friends. 他不善于交友。
She is an introvert and not good at making friends. 她是个内向的人，不善交友。
He is shy and not good at making friends. 他很害羞，不善交友。