Website is taking a cache

Hello,

It’s most important for me, I have customized something in PHP and CSS files.
But now I am not able to see my changes. Because it’s taking the CSS cache, according to me.
Now I am worried, if I delete the CSS cache, it will take a negative impact on my website. Can you please let me know, What should I do So that my website is working with my new changes?

Thanks

The page I need help with: [log in to see the link]