Try rebooting your PC or Reinstalling Roblox Studio or You can reset internet options in internet explorer so all your internet settings which create issues are reset back to factory settings.
Try looking for scripts that are not useful and delete them
Try and see if you can find “while true do” loops. These can cause a lot of lag to your game if you don’t add a wait at the end of the loop. It can be wait(0.1).
See and scan for viruses that could be lagging you game.
Last option, maybe you don’t have enough internet to publish the game. It can be a computer problem.
I already got rid of all useless scripts, meshes, unions and models before, the game is lag free now as it went from 48Mb to 20Mb and I don’t think I can remove anymore, and about my internet’s speed about 70-80Mbps, I am just to do a few changes not even adding some models or scripts and all of a sudden it doesn’t let me.