Actually, HTTP/2 was disabled some time ago. We were seeing issues where pages with a large number of assets (like image galleries) resulted in a substantial part of those files not being loaded successfully. Also, when disabling HTTP/2, we actually saw a substantial performance increase on sites that used HTTPS.
And no, you cannot enable HTTP/2 with .htaccess codes.
If you want to know more about how that went, please see this topic: After installing free SSL certificate from Control panel, website not loading fully
When I check the loading time graph of your site, I see that the overwhelmingly large part of the page load time is taken up by the WordPress PHP code executing:
If so, things like minifaction, compression, inlining provide a marginal benefit at best, and dramatically slow down your site at worst (if these “optimizations” are done on the fly with PHP code).