When you set z-index, try to set them for SIBLINGS elements and as high as you can.
For instance, select your whol navbar element (navigation section), the one just behind the symbol, give z index of 2. Select the section underneath, the whole section (fixture…) sibling to the navbar element, give it z index of 2.000.000, no I’m kidding 
just give it z index of 2. And then it works.