You might been browsing the internet by searching how to ungroup your units. Or you just started playing and you’re new to the game. Here some tips that might help.
Guide to Group and Ungroup Units
How to Group Units
Select required units (you can also mix types) and press Ctrl+1 (or any other number that goes on your keyboard, even on numpad). Now you created a quick access group for selected units.
To access your group now just press “1” (or the number you set by yourself). Double press “1” will not only select, but also focus on your group.
How to Ungroup Units
You just need to press ctrl+”group number” while no unit is selected.
Example: Ctrl+1 while nothing selected. That will delete the group.
How to Merge Groups
If you have more than two previously created groups 1 and 2, you can merge them by pressing shift+2 or create a separate merged group by pressing shift+3 (any unused number) while desiring group/units are selected.