[I would like to change the nether 1.16.4]

I created the server after 1.16.4 and im in a basalt unending biome its crazy i traveled like a 1000 blocks in the nether and its unbeliveable how giant this biome is and beacuse of that i want to change it is there another way to do it for 1.16.4?

 

[I would like to change the nether 1.16.4]

me and my friends started an SMP and we have a rlly bad nether that we would like to change and i tried to delete the file of the nether it worked but it just like reset the nether but didnt change him any ideas?