I am trying to make a very simple display time project for practicing my coding skills, the main implementation logic is completed, but there is a tiny problem is that I want to implement a fancy way to let the digit slide with a animation effect, but it failed

My scrollHandler function works just fine, when I’m on PC or when I open responsive inspect, everything works as it should, but when I open the application on a mobile phone, MENU always has the sticky property.

I have an image, I removed the background with a logiciel but when it appear in html it seem like a default background it applied to it like this :
here is the code for the image :

Below is a simple code, the essence of which boils down to the following: at the top of the page there is a shadow and if you scroll the page vertically, this shadow will be constantly visible, covering the components (except VideoComponent ) that are located in the div with id=’sub’.