Lightbox is under layers of other element of an self-hosted video

I am working on adding a self-hosted video on my website through HTML embed. I want the video to play on a lightbox when the image overlay is clicked. I am close to achieving this but my problem is that the lightbox is under the other elements, so when I scroll the page it is covered with all other elements of the page. Please click only the first video with logos beside it.

Here is my site :