Hello,
1/ As I can see, CDN is used on your site – https://gyazo.com/a75afa3ee408cef848c9ebe933315693 If you do not know about it, try to contact your hosting provider.
2/ Try to disable all the third-party plugins (including cache plugins), that do not come bundled with XStore https://xstore.helpscoutdocs.com/article/36-included-plugins , clear cache of browser, and check Categories then.
3/ Provide temporary wp-admin access, so we can take a closer look.
Regards