Instruction for Ubuntu 20.04

As you can see in this picture you can go to setting,then Select Appearance then select auto-hide the dock and slide it to enable. If you want to hide the top bar to get better screen view.

1.) Press Ctrl+Alt+T on keyboard to open terminal. Then run the apt command to install the extension:

sudo apt install gnome-shell-extension-autohidetopbar

Type user password for sudo prompt and hit Enter. 2.) Once installed, restart Gnome Shell by pressing Alt+F2 and type r in the pop-up “Run a Command” box and hit Enter. 3.) Finally open either Extensions or Gnome Tweaks (both available to install in Software), and enable “Hide Top Bar” extension.

It was a useful find for me , now I'm enjoying the full screen mode for coding and browsing.

Instruction for Ubuntu 22.04

1. Open terminal ctrl+alt+T and do a update -> apt update
2. If not a root user then use sudo

   sudo apt install gnome-shell-extension-manager -y
   

3. click on show applications
4. search for Extensions Manager and open it.

1. Switch to Browse Tab
2. Search for hide top bar
3. Install the one that is enabled and supported.
4. Switch to Install Tab to see the Hide Top Bar and enable/disable to check it out.