After I update to Unity 2017.2 there's a error, no matter what I do it can't get fixed, I tried to remove the dll file it doesn't work I also tried to delete the library and it doesn't work either

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1

error CS1704: An assembly with the same name UnityEngine.Timeline' has already been imported. Consider removing one of the references or sign the assembly C:/Program Files/Unity/Editor/Data/UnityExtensions/Unity/Timeline/RuntimeEditor/UnityEngine.Timeline.dll (Location of the symbol related to previous error) Assets/Club/1.1/Test Level_RPG_Data/Managed/UnityEngine.Timeline.dll (Location of the symbol related to previous error) error CS1704: An assembly with the same name UnityEngine.UI’ has already been imported. Consider removing one of the references or sign the assembly
C:/Program Files/Unity/Editor/Data/UnityExtensions/Unity/GUISystem/UnityEngine.UI.dll (Location of the symbol related to previous error)
Assets/Club/1.1/Test Level_RPG_Data/Managed/UnityEngine.UI.dll (Location of the symbol related to previous error)
error CS1703: An assembly System' with the same identity has already been imported. Consider removing one of the references Assets/Club/1.1/Test Level_RPG_Data/Managed/System.dll (Location of the symbol related to previous error) System.dll (Location of the symbol related to previous error) error CS1703: An assembly System.Core’ with the same identity has already been imported. Consider removing one of the references
Assets/Club/1.1/Test Level_RPG_Data/Managed/System.Core.dll (Location of the symbol related to previous error)
System.Core.dll (Location of the symbol related to previous error

2

You have created a standalone build into your assets folder. This is messing your whole project up. Never create a build inside your assets folder. Unity will try to import everything that belongs to the build into your project.

So delete this folder completely:

"Assets/Club/1.1/Test Level_RPG_Data"

This is the _Data folder of your build. If you build your project you can create a “builds” folder next to the Assets folder but never inside.