Why my static React website is freezing in localhost?

I created a static React website, there is no database, no node.js, no login system. It is a simple company website with many SVG images and a lot of CSS work. I made it with Bootstrap 4. But when I try to run it on localhost it freezes many times. I am unable to figure out why the website is hanging, also it takes time to load all the SVG images.
Can anyone tell why does it freezes?