Responsive Website make of using HTML ,CSS & BOOTSTRAP.

Just set your background to a dark color.

You are not alone with that white flash problem. Everyone who attempted this project experienced this problem. I also could not find how to fix it, although I do know why it happens.

It happens because when your website is loaded for the first time, it has to load all the images and other assets. When this happens for the first time, the assets are loaded a little later than the body of the web page, thus what appears as a white flash is just the white body of the webpage which is covered by the background image as soon as it gets loaded.

I would advise you to not get into that stuff. Your website is already looking pretty neat, what you can do instead is make the website with React so that it does not reload every time a link is clicked. It would be a great upgrade and could very well become your first step in Javascript Frameworks.

You can also make the buttons round in CSS if you like with the border-radius of 50%, and make the height and width of the buttons equal. I would look much better that way and would be way closer to the original design.

Hope these suggestions would help😊.