In a module such as Deals/Opportunities there is related fields at the top of a record. These can be adjusted to view different fields as required.
Open any record in the module changes are required
Click on the three dots ( . . . ) in the far right of the screen, just below your account icon (or photo if you have uploaded it)
4th item from the bottom is ‘Customize Business Card’
You can have up to 5 fields in your business card, select and delete until you have the desired fields – Save
Note that when you hover over the contact/owner details you will see a pop up with further information