1Don't do that , just don't.
2you'll have regrets a lot of it.
3And I'm serious.
4A lot of things will deleted,but by the way, if you already done that don't worry, there is a solutions.
5Just run this code in your terminal
6
7sudo apt install ubuntu-desktop
8And if you want you can run this one too
9
10#ubuntu-18.04.1
11sudo apt install $( curl http://releases.ubuntu.com/18.04/ubuntu-18.04.1-desktop-amd64.manifest | sed -e 's#\t.*##g' )