I'm sorry you're struggling, MoonSunn. I know how it feels to not know how to engage with people anymore, forgetting what it is they talk about. Looks like a lot of other people here have had similar experiences.

Sometimes, as hard as it is, doing more with people can help with that exact problem. Even if it's awkward at first, the more you do, the more you'll have to talk about the next time you see them. Talking about shared experiences and things that are similar to those shared experiences is one of the building blocks of social interaction. ("Remember when we did X? Well, I did X again with...") The advice Fizzyo gives to ask other people about themselves is really good, too.

It can be so hard to get back into the swing of things. To remember how to connect. To break down the walls depression builds around us. All we can do is keep trying. Please remember you're not alone in this struggle.