How to get underline while hovering over the menu

[iHavPet]

Like this website has it: https://calitheshop.com/

[iHavPet]

https://6a0203-f3.myshopify.com/

[iHavPet]

It worked but know i have 2 lines with some buttons black and blue line. How i can fit this?

[iHavPet]

Okay so basically if i hover over the menu buttons there needs to be only one underline. the underline color doesnt matter

[iHavPet]

Yes it worked but i need now footer also and then it will be done