Forge Server won't start

Hello, I got a forge 1.12.2 Server that won’t start. I got these mods:
Chisel, Chisels & Bits, CTM, GravityGun, Ice and Fire: Dragons, LLibrary, Mekanism, Mekanism: Tools, Mekanism: Generators, Pam's Harvestcraft, PortalGun, SCP: Lockdown, SecurityCraft, RealTrainMod, NGTLib, iChunUtil

Here’s the error:

A problem occurred running the Server at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source) at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source) at java.base/java.lang.reflect.Method.invoke(Unknown Source) at at net.minecraftforge.fml.relauncher.ServerLaunchWrapper.main( Caused by: java.lang.ClassCastException: class jdk.internal.loader.ClassLoaders$AppClassLoader cannot be cast to class (jdk.internal.loader.ClassLoaders$AppClassLoader and are in module java.base of loader 'bootstrap') at net.minecraft.launchwrapper.Launch.<init>( at net.minecraft.launchwrapper.Launch.main( ... 6 more

The error also comes when I try to start it via MultiMC. I got the forge version on MultiMC and also on the server. Do I have to use another version or does someone have a solution for that?
By the way, I also have the same error in MultiMC.