My prefix worked very good, but last time i joined my server my prefix was gone, i typed "/lp user Freeze_Line info" and i had prefix "Owner" but when i typed "hi" i saw this "[world]<Freeze_Line> hi" i don't know what happend and what to do.

LuckPerms does not handle the chat. Your chat plugin does. So there's an issue with your chat plugin, not LP (as you demonstrated with the /lp user Freeze_Line info command).

Reach out to the support of your chat plugin.

I will try it, thank you

But i don't know why it stopped working, it worked before.

Neither do I. Though this isn't the right place because LP clearly still works as intended.

I have only one chat plugin "EssentialsXChat"

And i don't have a map for this plugin

Do i have to uninstall EssentialsXChat?

What map are you talking about?
You are supposed to reach out to their support.

But how do I supposed to reach their support?

I have never asked for support for my server

https://www.spigotmc.org/resources/essentialsx.9089/

Google is a thing too.

What does /ess version show you?