In your style.css make these changes:

.navbar {
     z-index: 10;
}

#about{
     z-index: 5;
}

What does that mean?

The value of z-index is more in navbar than in about section. More z-index value will give it more priority and it will be positioned on the top.

Read more about z-index at https://www.w3schools.com/css/css_z-index.asp

the first – you should handle images or gift or video size and convert to for web types because
your web site very big size and delay for loading ,

the second – Adding this might solve your problem

.navbar {
   z-index: 9999
}

navbar disappears in second section. tried everything but does not work. I am not into coding btw. just complying to a subject requirement here is the file to get a better look

tried everything I understand at my level. it is driving me crazy.