How to edit the nav-menu (or how to make it disapear…)

Hi the support team, I just can't figure how to edit the nav-menu which is on top of the float images. The Appearance => Menu option doesn't show any menu to be edited and I don't understand why some page titles are getting in this menu and other aren't. In any casse, I'd like to be able to edit it freely. If it isn't possible, how could I delete it (or have it disapear) ? I've tried a few things and searched the forum for answers but could'nt find any with my limited abilities. If needed, here is the URL : https://alzabox.000webhostapp.com/ It's still to be sorted and edited but I'm sticking to this first matter. Thanks in advance for the answers, keep up the fantastic work. Dara