Backbiting : doubts on it

Assalamualaikum, recently, i have learned that backbiting is a major sin. I have doubts on it & some more issues added based on islam.Here they are: Doubt 1. If i backbit someone accidentally or intentionally, do i have to reach out to them even if it's awkward because they don't know me and they are out of my reach? Let me give you an example. My friend had talked about a neighbour living next to us- we both know him. She talked some things about him- though i wasnt sure she would talk bad things or so. Also, I had listened to her words so i bear the same sin as her but its unintentional and accident. What do i do? Also, even if jt is backbiting, Its awkward to seek forgiveness because he doesnt know us since we are strangers. He might get shocked and mom warned us not to talk or visit any strangers house, so it's not possible to ask forgiveness however. Am i forgiven if i just ask forgiveness from Allah?