Placing menu in header

I have created a drop menu from container boxes and buttons. The drop down container boxes are hidden until one of the main menu items is hovered over.

I have a thin header at the top of my page which I want to place this entire menu in. However, wix is making me widen the header to be able to fit the complete menu in, before I can place it there. I only want the header to be as wide as the top container box of the menu. I hope this makes sense - here is a screen shot to clarify…