Impossible to load my website (made with Highend WP theme)

Hello,
I noticed that very often, after I updated my Highend WP theme from the WP Admin Panel, I receive this kind of notification from my website:
“Hi Innovativetransmedia,
Jetpack Monitor is on the job, keeping tabs on http://www.innovativetransmedia.com. During our last check on Monday, July 21, 1:19 pm, we noticed that your site was down.
If you’re concerned about your site’s status, you might want to get in touch with your hosting provider. We’ll continue keeping track, and will let you know when your site is up and running again and the total downtime.”

and again, via email:

“Good news” your site http://www.innovativetransmedia.com is back up! Your total downtime was 8 mins, but your site was up again as of Monday, July 21, 1:27 pm. If it goes down again at some point (we hope it doesn’t!), we’ll be in touch.”

– After the update I had this message displayed: “Briefly unavailable for scheduled maintenance. Check back in a minute.”

– Then I noticed my website is super-slow, sometimes it takes more than 60 – 90 seconds to load the homepage…

I just tried to open the homepage from different computers, different browsers (Safari, Firefox, Chrome) and also from an iPhone browser, and of course I previously emptied caches, cookies and everything… and the result is still and always the same: please see the Screenshot I took from Safari, attached hereto

That is really weird, it’s impossible for me to access it.

Please let me know what you think,

Thank you