I changed the spawn world and now the server won't even start

[KatieSquare821]

I wanted to make a skyblock server. I downloaded a map, opened it in Singleplayer first to change the version of the world to 1.14, I even used the "Optimize world" option. I packed the world in a .zip file. I uploaded the world on the server successfully, I could also access it using /worlds command. I set the worlds spawn on the map I uploaded. I exited the server and I stopped it. Then in the server panel, I changed the Level Name to ul_(name od the map). I waited for the server to go in hibernation. Then I activated it, and I tried to make it start. I click start, it's loading for a while, and then it just says "offline". I went into the danger zone to repair the files. After that my uploaded world often disappears. Or, despite setting it as the default world, I still appear in the "normal" world (not the one I uploaded).

[PandaChan]

If you want to spawn in the uploaded world you need to change the level name in server properties to the name. 

[chrisgauthier9]

Where do you go to do that