Hi Rene,
It is possible that not all of the links on your site are not updated to https which is causing the slow loading page although I cannot confirm this for now because when I tried to check your licenses page, I don’t see any domain registered to the license you have.
Kindly make sure that all instances of the site non https site links on your site are updated to https. To do this, you may check using the Better Search and Replace plugin then search for the following:
http://example.com and replace with https://example.com and
http:\/\/example.com and replace with https:\/\/example.com
Please replace example.com above to the domain of your site. Also, please make sure you keep a full backup of the database before making any changes.
I am not sure if you have checked the article linked by @paul.r but not all information there are basic. Some suggestions there are advanced that a non tech person might not be familiar with. It would also be possible that some of the trips included in the article are not applied to your site yet.
Also, please note that the support we offer is limited to the theme setup and possible bugs if there is any. Customizations and optimizations are beyond the scope of the support we offer but we will be happy to check your site in case you are still having issues with it. Please provide the URL and admin details of your site in a Secure Note so that we could provide more accurate suggestions.
Thank you.