Finally i solved this error.
So How can you solve this error.
First, go to C:\Users\[User Name]\AppData\Local\Xamarin\zips directory. AppData is hidden folder. You must select show hidden folders from folder options.
Delete all of the zip files.
Open Visual Studio and create a new project
Update Xamarin Forms from Nuget Package Manager
(You have to update Xamarin Forms for every project)
Right Click on the projectname.droid from solution explorer then select clean solution and build solution respectively.
Now Visual Studio is going to download the support packages which required for Xamarin. My computer downloaded the 200MB in size zip file.You should be patient. it was take 45 minutes at my pc.
(if you don’t update the Xamarin Forms every project. Xamarin will download the support package for current version.)
After the downloading packages. Build will complete and you can start develop your app