Can't upload a world, and the "progress bar" doesn't show up.

Hello! i had a world with my friends, and one of them entered an "illegal" zone. i tried fixing the things he left, but it was too much so i decided to download WorldEdit to Copy from the original map and Paste it on our current one. I already saved the .schem file, but now when i try to upload a world, my computer has some extreme lag on the first 2 or 3 mins, and then the loading cog shows up on the world. The thing is, seeing more of these kind of threads showed me there's a "progress bar" which i never see, and it sometimes just shows this "Oh No!" error that says the website cannot be loaded and the world doesn't load. already trying loading the .zip file of the world 3 times, nothing happens. please help ?

i tried both.

i'm using Google chrome, but i could install any browser for testing.

So i've been reading some threads and they say to use this "Legacy" system, how can i use it?

ok, i tried it, and the progress bar actually showed up. but when it finished, it said "An error ocurred!" and that's it.

changed computer and browser (Mozilla). It didn't work, but this appears in console:
world upload failed: Error:"Lost connection to Websocket"
Connect https://aternos.org/panel/js/c…n.bundle.js?v=24012020:25