Thanks for the video.
Did you make changes to template files?
Ajax search result speed depends on server response time and DB structure. Theme sends requests to your DB and waits for response. So, if it’s slow, try to speed up the server response time. We can do nothing with it.
About site speed – https://xstore.helpscoutdocs.com/article/100-how-to-speed-up-my-website
Regards