Slow load times moving site from http to https

I recently purchased ssl certificate through register.com and made the jump to convert from http to https. They installed and gave me instructions on code to enter in htaccess file to redirect from http to https. After completing the task it seems my load times have increased dramatically. Any help or insight to why this may be happening and methods to resolve would be greatly appreciated. They are not much help on their end so I am just reaching out for guidance. I am really considering hosting with Webflow(Easy quick publishing and tired of support at Register.com) but afraid to make to the jump because of the possible loss of search engine ranking due the the process. Is this just a myth? This might be a stupid question and request for help, but I know just barely enough to build a site on the platform and upload it to the server. Also, are there experts on Webflow that can help you make the transition and guide you through the process of switching from one host(register.com to Webflow)? Thanks for your time and any help that may be out there.

Website:

www.trinityrvrentals.com