How to add links in header.php on a wordpress site?

Question

PHP

Hello! There is an online store on wordpress. It was necessary to add buttons-links to other resources in the header of the site. The first 2 buttons are links to other sites and the remaining buttons are links to html pages. Unfortunately, my knowledge of php is very superficial, so I added these buttons using regular html in header.php. When everything worked out, my joy knew no bounds until yesterday, until I accidentally discovered that links to html pages work only from the Main page of the site, from any other page, and also from the page of any product, these links do not work. In general, help, whoever can... An example code for a link button to an html page:

<button class="button button--ujarak button--benetton button--border-thick button--text-upper button--size-s button--inverted button--text-thick" onclick="window.open('benetton/index.html', '_blank');" title="Перейти на сайт BENETTON">Benetton</button>

Answer 1

give a link to the site