How to start and hold conversations?

I don't know if it's a result of something mental like ADHD, (which I think is definitely possible that I have it) but I can't conversate normally and it's seemingly worsened in recent years.

If someone asks me something I'll respond and sometimes I'll say it quick and I'll pronounce it wrong, or I'll just completely forget what I was going to say and fumble over my words.

Sometimes I will try and think of a conversation topic during silent gaps in the chat and I'll go completely blank and be unable to answer so it'll be silent and awkward until I think of something or they continue talking.

I'm just looking for tips, conversation starters, anything that will help.