what will you do if you saw your best friend's husband dating another girl?

To be honest, I don't know what I would do in such a situation. I probably wouldn't interfere in other people's relationships. I can only advise single people to this article https://omtimes.com/2020/06/older-people-soulmate/ so that you can understand what ways there are on the Internet to find a soulmate. These helpful tips are sure to help you get rid of loneliness pretty quickly.