Hey Prenji ,
As you are having multiple Menus and the structure of the theme is designed in the way that the logo and the menus and the cart menus are all aligned in one line so the width is taking default distributed width.
If you want to make the menus in one line then either you will need to change the number of menus or else you will need to change the design of the header accordingly.
This is an accepted solution.
Your header navigation don't have enough space to accommodate all menus and that's it's messed up. So either you increase the navigation width to have it accommodate more menus (which down't look feasible as number of menus are more) or reduce the menu items. Menu items like Ship Internationally, Ship to Canada can be grouped in About Us and for Social Media Menus like Instagram and Pinterest you can add them as two new sections on home page and show feeds directly. Or add them as icons in the Nav. That way you will be able to save enough space for your other menus.