I have optifine, I'm using 13.9 C&B on 1.11.2.

I got a crash report. I don't know what it was. But I'll just put it under this.

---- Minecraft Crash Report ----

WARNING: coremods are present:
Contact their authors BEFORE contacting forge

// This doesn't make any sense!

Time: 5/23/21 9:20 PM
Description: There was a severe problem during mod loading that has caused the game to fail

net.minecraftforge.fml.common.LoaderExceptionModCrash: Caught exception from Chisels & Bits (chiselsandbits)
Caused by: io.netty.handler.codec.EncoderException: java.io.EOFException: fieldSize is too long! Length is 28276, but maximum is 175
at net.minecraft.network.PacketBuffer.func_150793_b(PacketBuffer.java:316)
at mod.chiselsandbits.client.ClipboardStorage.read(ClipboardStorage.java:95)
at mod.chiselsandbits.client.CreativeClipboardTab.load(CreativeClipboardTab.java:31)
at mod.chiselsandbits.core.ChiselsAndBits.preinit(ChiselsAndBits.java:141)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.minecraftforge.fml.common.FMLModContainer.handleModStateEvent(FMLModContainer.java:647)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.sendEventToModContainer(LoadController.java:253)
at net.minecraftforge.fml.common.LoadController.propogateStateMessage(LoadController.java:231)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at com.google.common.eventbus.EventSubscriber.handleEvent(EventSubscriber.java:74)
at com.google.common.eventbus.SynchronizedEventSubscriber.handleEvent(SynchronizedEventSubscriber.java:47)
at com.google.common.eventbus.EventBus.dispatch(EventBus.java:322)
at com.google.common.eventbus.EventBus.dispatchQueuedEvents(EventBus.java:304)
at com.google.common.eventbus.EventBus.post(EventBus.java:275)
at net.minecraftforge.fml.common.LoadController.distributeStateMessage(LoadController.java:148)
at net.minecraftforge.fml.common.Loader.preinitializeMods(Loader.java:647)
at net.minecraftforge.fml.client.FMLClientHandler.beginMinecraftLoading(FMLClientHandler.java:276)
at net.minecraft.client.Minecraft.func_71384_a(Minecraft.java:440)
at net.minecraft.client.Minecraft.func_99999_d(Minecraft.java:352)
at net.minecraft.client.main.Main.main(SourceFile:124)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:497)
at net.minecraft.launchwrapper.Launch.launch(Launch.java:135)
at net.minecraft.launchwrapper.Launch.main(Launch.java:28)
Caused by: java.io.EOFException: fieldSize is too long! Length is 28276, but maximum is 175
at io.netty.buffer.ByteBufInputStream.checkAvailable(ByteBufInputStream.java:253)
at io.netty.buffer.ByteBufInputStream.readFully(ByteBufInputStream.java:174)
at java.io.DataInputStream.readUTF(DataInputStream.java:609)
at io.netty.buffer.ByteBufInputStream.readUTF(ByteBufInputStream.java:228)
at net.minecraft.nbt.CompressedStreamTools.func_152455_a(CompressedStreamTools.java:126)
at net.minecraft.nbt.CompressedStreamTools.func_152456_a(CompressedStreamTools.java:87)
at net.minecraft.network.PacketBuffer.func_150793_b(PacketBuffer.java:312)
... 40 more

A detailed walkthrough of the error, its code path and all known details is as follows:

-- System Details --
Details:
Minecraft Version: 1.11.2
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_51, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 171522736 bytes (163 MB) / 436207616 bytes (416 MB) up to 6442450944 bytes (6144 MB)
JVM Flags: 8 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xmx6G -XX:+UnlockExperimentalVMOptions -XX:+UseG1GC -XX:G1NewSizePercent=20 -XX:G1ReservePercent=20 -XX:MaxGCPauseMillis=50 -XX:G1HeapRegionSize=32M
IntCache: cache: 0, tcache: 0, allocated: 0, tallocated: 0
FML: MCP 9.38 Powered by Forge 13.20.1.2388 Optifine OptiFine_1.11.2_HD_U_B5 7 mods loaded, 7 mods active
States: 'U' = Unloaded 'L' = Loaded 'C' = Constructed 'H' = Pre-initialized 'I' = Initialized 'J' = Post-initialized 'A' = Available 'D' = Disabled 'E' = Errored
UCH minecraft{1.11.2} [Minecraft] (minecraft.jar)
UCH mcp{9.19} [Minecraft Coder Pack] (minecraft.jar)
UCH FML{8.0.99.99} [Forge Mod Loader] (forge-1.11.2-13.20.1.2388.jar)
UCH forge{13.20.1.2388} [Minecraft Forge] (forge-1.11.2-13.20.1.2388.jar)
UCH mercurius_updater{1.0} [mercurius_updater] (MercuriusUpdater-1.11.2.jar)
UCE chiselsandbits{13.9} [Chisels & Bits] (chiselsandbits-13.9.jar)
UCH worldedit{6.1.6} [WorldEdit] (worldedit-forge-mc1.11-6.1.6-dist.jar)
Loaded coremods (and transformers):
GL info: ' Vendor: 'NVIDIA Corporation' Version: '4.6.0 NVIDIA 456.71' Renderer: 'GeForce GTX 760/PCIe/SSE2'

There's the crash thing. Anyways, please reply in what the heck is going wrong.

1.12.x is not supported anymore.