Server Crash (Optifine 1.16.5) WE NEED HELP

Every time we try to start our server, it always crashes. I don't understand what the errors mean. Here's the link to our logs:

https://mclo.gs/n98vYzI

What do I do with this code to fix it?

We tried it, but unfortunately, it still didn't work. Our server still crashes. Maybe you have more suggestions? Thanks in advance!

My bad. Here it is:

https://mclo.gs/2nHtjWR

http://ClassicsClub.aternos.me

We don't know. We haven't tried removing the plugins.

Still didn't work. Here's the new log:

https://mclo.gs/Y69PaPz

Still wouldn't budge. Here's the new log:

https://mclo.gs/KI06Lx9

It worked, but not in the way we hoped. The server is not crashing anymore, but our hard-earned progress is now gone and we have to start a new world. Is there a way to fix both the server crash AND keep our progress at the time before the aforementioned crash occurred? (Don't worry, we kept a backup of our world just in case.)