Looks like that site is using Bootstrap. The best solution I can see is edit the column classes of both the right side:
"ep-geo-navigation__welcome-block col-md-4" should be "ep-geo-navigation__welcome-block col-md-5" -- to take up more of the screen
and the following div has:
"col-md-8" should be "col-md-7" -- to take up less of the screen