How to make any groupe full screen

I need help with making a group on the page the full width of the page.
so that I can have an Icon from google Material and when that icon is clicked a specific group on the page takes the whole screen.
for example say someone is doing something an the app, the page has a lost of different stuff on it, but then an Icon that say do not disturb or peace mode or quiet mode, and a specific group takes over the whole screen. a Group that I choose on the backend.