Minecraft player data is always reset after world join?

I have the problem that if I insert a map downloaded from my server into saves and want to play it in single player, everything is as it is on the server, only the player's inventory and the spawn point in the world, i.e. The player data is always reset will as soon as I enter the world. How can I fix this?

Series of images:

I don't think that can be fixed, but I'm not sure.

Thanks for pointing this out, but you can. I found the solution to this yesterday. https://www.reddit.com/...move_your/