Change your JVM to Eclipse J9:
Download
While installing remember where's it installed, in my case its: C:\Program Files\AdoptOpenJDK\jdk-8.0.265.01-openj9
Now after installing done open your minecraft and go to your Change JVM Executable or Java Executable
Now change folder to your install location with jre/bin/javaw.exe
It should looks like that: C:\Program Files\AdoptOpenJDK\jdk-8.0.265.01-openj9\jre\bin\javaw.exe
Now you can set ur Java Arguments i recommend you to use only -Xmx<how much ram allocate> for me its -Xmx7G only, no other parameters because game can ocassionaly crash
Change your Forge settings:
If your game started Go to Mods, Click on Minecraft Forge and click Config on left bottom, click Client Settings and change "Force threaded chunk rendering" from false to true
Now your game should work better
