I'm going to try to keep this as short as possible, but if you need any additional context or information, don't hesitate to ask. Also, if this is not the correct SE platform for this question, please point me in the right direction.
Can the server admins / ISP / anyone else read the content of my Gmails, WhatsApp Web messages, or any other communications on platforms that use HTTPS?
My understanding of HTTPS is that it is not possible but I'm not entirely sure.
All communications that use HTTPS protocol means everything is encrypted between you and the server (remote end) so right out of the box they can't read your information. If you store the information locally (on your computer) applications create databases to store information and they probably could play with that to make it readable but if you are just on the web from your phone/computer you're safe. Also, the ISP can only see the traffic/domains you're visiting but not the actual content.