dnSpy - How to fix Multiple Assemblies error

Dear dnSpy users, have you got Multiple Assemblies error? Well it's very easy to fix. When you compile, look closely at error descriptions, it does tell you which .dll files are duplicated. Example: System.dll and mscorelib.dll is duplicated

Actual error:
Severity    Code        Description File        Line
Error       CS1703      Multiple assemblies with equivalent identity have been imported: 'C:\WINDOWS\assembly\GAC_MSIL\System\\<name>.dll' and '<path of game>\Managed\<name>.dll'. Remove one of the duplicate references.

Removing assemblies from dnSpy won't help because it adds them back automatically
Close dnSpy and delete the duplicated .dll files from Managed folder that dnSpy mentioned

That's all. You are good to go. Open dnSpy and enjoy modding without error J

Video tutorial: