Can't keep up! Is the server overloaded? (BetterMC 1.20 GPortal Server)

I've been experiencing massive lag on my Minecraft server for two days. The CPU isn't overloaded and 10GB of RAM should actually be enough. My theory with friends was that it's because it's trying to load too many chunks, but I'm not sure about that anymore.

Attempts I've made to fix it:

1. Contacted Gportal support, but they said it's not a hardware problem on their end.

2. Contacted BetterMC Admins, but that didn't help either.

3. Lowered server tick rate, view distance, and simulation distance.

4. Tweaked a lot of things on GPortal.

5. Changed Java version.

Here are the logs in case they help: https://mclo.gs/NwybMKE and Spark Profile https://spark.lucko.me/9jgfHOuHKI