How do you even manage a convo over text anyway?

I’m socially incompetent and I’m trying to befriend someone new I met. I have their number and I was thinking about inviting them to do smth, but I have literally no idea what to say/how to phrase it so that it sounds cool.

How do I know what to text people in general?

Also one of the hardest things to me with texting is knowing when a convo is done. Where do I leave it/when is the convo finished? Sometimes I get my feelings hurt if there’s no reply back to what I said, so I have a bad habit of just over texting. Is it fine to just dip in and out randomly?

I know this sounds dumb but I am socially very dumb. I lost contact with all my friends over the pandemic and kind of forgot how to text, so any tips appreciated.