Change default user to use sudo on Gnome [debian]
 

I created a user account (first account) which is able to use sudo command and disabled root account during debian 9 installation. Then I created a standard user account (second account) for everyday use. Then I decided to give that standard account authority to use sudo as well.

Now when Gnome tries to upgrade the software on my system, it always asks the first account's password.

How can I make it ask the second account's password?

sudo always asks for the password of the current/actual/logged in user.