GUI Performance Monitor Tool
Solution 1:
You can use the default System Monitor. Launch it from terminal with gnome-system-monitor or search for System Monitor/Task Manager on the search window in the sidebar. If you prefer to use terminal based system monitor, try htop or nmon
Solution 2:
A particular flavor of top that we use here is htop. Still CLI based but much more 'graphical'.
Install it with:
sudo apt-get install htop