The menu font styles (some of which are narrower than others) and size can be adjusted in the customizer, which may make it narrower for you. Adjusting the spacing b/t items would probably take custom css coding (I know some basics, but beyond my current knowledge).
Keep in mind that even if you get the items to fit on one line, it will still spill over on a mobile device.
One way to approach this latter issue within Make is to put 1-3 high-priority menu items in the header bar, in addition to having your full menu in the standard location. See davewheitner.com for an example of this, where I’ve put two items I want to make sure people see right away in the header bar. Hope that helps!
Oh, keep in mind too that within the menu editor, you can edit the name of the menu item so it’s shorter than the title that appears on the page itself. This may enable your menu to fit.