I do want to note that this shouldn’t affect anything on your system. I have taken from GUI to Core multiple times and never have had an issue yet. If you have please comment blow so I can add a warning to this post. Yes you can go from Core to GUI. Check out this post.
1. You want to open up PowerShell and type in the following command:
Uninstall-WindowsFeature Server-Gui-Mgmt-Infra -restart
2.5 I also noticed at the 30% mark you will hit a black screen. Do not be alarmed by this it is just changing your features.
3. Once the black screen comes back you will see the normal restart screen again.
5. After it has restarted you will directed to the Core.
You don’t feel like using PowerShell?