and how to trade with AI if you play alone?

There are several variants, but all of them are tedious right now, because it requires manual configuration.

1. https://mods.factorio.com/mod/AITrade (some stuff won't work)
2. Create a new force via /editor and sell/buy stuff with endless chests on new surface (very tedious and not perfect solution)

I have an idea, but it is impossible to make a global market using the API address of factorio servers, for single players too. For example. sell and make sums of money.

but it is impossible to make a global market using the API address of factorio servers

There's one mod developer who's trying to do that and, also, my mod is accessible via rcon, so there are ways for such idea.

Try https://mods.factorio.com/mod/trading_system instead