Keeping Navigation menu centered and responsive

Hello fellow community.

I have a website using Customizr: grasklipparservice.se

And I want the page to be centered to the middle – I have solved the logo, the pages and so on – but every solution I found to center the menu screws up something else – and the way it looks now is dull 🙁

Do anyone have any good solution?
Can I activate the menu adapted for smaller screens(like smartphones) for every screensize?
Is there any good menu plugin that I could replace the navigation menu with?

(I have searched the forum for this without success – so if anyone found a good solution, please share and don’t be offended because I create a new topic 😉 )

Cheers,
David