Menu on mobile dosent open + scale problem

hi hello he-ya
first time building website for a client - and ever…needs your superior help!

1th question:

  • the when in mobile mode the drop down menu dose not open at all…it is in fixed position and still nothing.
    how can i make it work?

2th question:
fallowing that how come what i see in the preview mode looks different after published?
for example the blank space in the bottom of the screen dose not appear in the preview mode 1920 but when i open it in my browser the blank space is there , same with mobile…what am i missing here?

much obliged dear elders of the internet!