Answer by xsushil for Error retrieving parent for item: No resource found that matches the given name after upgrading to AppCompat v23

If you are getting errors even after downloading the newest SDK and Android Studio, here is what I did:

1. Download the most recent SDK
2. Open file-Project structure (Ctrl + Alt + Shift + S)
3. In modules, select app
4. In the properties tab: Change compile SDK version to API 23 Android 6.0 marshmallow (latest)

I hope it helps someone so that he won't suffer like I did for these couple of days.