Hello, Pedro Monteiro,
1/ We can see that menu elements are already in use, so you can try using an HTML block. To do this, go to Dashboard > Static blocks > Add new and create the desired content. Then, select this static block in the settings of the HTML block via the Header builder.
2/ Please refer to the attached screenshot for further information – https://prnt.sc/UnYoFzQ0itNp
3/ Header Builder > Dropdown menu > Computed Box > Border.
We hope this information is helpful.
Kind Regards,
8theme team