I don’t think that it is possible. The S in HTTPS stands for “secure”, which means that communications are encrypted. HTTPS is used primarily when there is important information that is being communicated between you and the website that you don’t want other people to know.
There is a type of cyber attack called a “man-in-the-middle” attack, which is when a malicious agent intercepts your communications, spies on them, and then passes them along to the final destination without either party ever realizing that he was there.
If communications were not encrypted, then a man-in-the-middle attack will be able to steal all of the information that is communicated. This would include email logins. In the process of setting up a Gmail account, the malicious agent could potentially steal your name, address, email address, and cellphone number. Many HTTPS websites involve monetary transactions, and that information could be stolen also.
A more severe version of the man-in-the-middle attack is when the communications are not only intercepted, but modified before being sent to the final destination. This means that you could think that you are viewing Google.com or any other website, but you are actually viewing whatever the malicious agent wants you to see. This opens the door to attacks in which you think that you are downloading something legitimate, but the malicious agent replaces the download with malware without either party noticing.
So, not only do you not want to turn off HTTPS, but it is very likely that the websites just won’t allow you to turn it off, since it represents a security breach.