Hello, @Linna,
If you are able to see the changes in Customizer and not able to see the changes after publishing it on the page front, then it means you are facing the cache issue only as if it is working fine in Customizer, it should have to work on frontend as well,
I have just checked your site as well, and the button color and title size both are changed on your site: https://postimg.cc/kVRP5VBV
Please try to clear the site and browser cache and check back OR try to check the site on any other Computer on a fresh new browser and I am sure you will not face this issue anymore.
Regards 8Themes Team.