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.

What does /ess version show you?

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.