First, fix your Code Errors. Some of them are critical.
https://validator.w3.org/nu/?doc=https%3A%2F%2Fwww.kasdivi.com%2F
Second, your fonts are coming directly from Bootstrap.css as expected, It's the last stylesheet in your stack which gives it highest priority. See screenshot.

Currently, these font-families are being used throughout your site.
--font-family-sans-serif: -apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,"Helvetica Neue",Arial,sans-serif,"Apple Color Emoji","Segoe UI Emoji","Segoe UI Symbol";
--font-family-monospace: SFMono-Regular,Menlo,Monaco,Consolas,"Liberation Mono","Courier New",monospace;
My browser's INSPECT panel (F12) shows a reference to Brush Script MT higher up in the stack (responsivelayout.css) but that's ignored. If you want to give it a higher priority than Bootstrap, move it lower in the stack. DO NOT EDIT BOOTSTRAP CSS!
Hope that helps.