Menu Building is completely broken

Menu Building is completely broken

I have been 3 hours, I have not been able to edit the menu. Either it is completely broken, very little intuitive or I do now know anything...

There is no way to create a megamenu, no way to create a menu. Despite the fact I go to menu configurartion and edit it the menu still remains the same, it is locked to categories. There is no way to change it