When you take the photo in "portrait" orientation, they come out sideways.
You need to take photos in "landscape" orientation.
Do you know, the screen dimensions are identical to a current television screen. It's just the size is smaller. Hold your phone up to your television screen and move it forward and backward until the edges of the phone match the television. They are identical in proportion. That's why photos really "should" always be taking in "landscape" rather than "portrait". Software programs don't recognize the "portrait" orientation, thus, flip them sideways.
When I do take a photo in "Portrait" and want to upload it or use it for posting on the internet, I always open the original in the old original "Paint" program, rotate the image 1/4 turn and resize the image to fit landscape. Resave to a new file name, and then upload it. I also reduce the size to make a smaller file size. The resolution on your computer will only produce so much, anything more is lost anyway. And so many programs and applications have file size limitations also, or will reduce the resolution when uploading to make a smaller file size. So I control all of this myself before uploading.
Also, I use a 3rd party hosting site, and then just use the link to post on here. For me this works. ... https://imgur.com/
.... is completely free.
Me and my little boy ... Fort Belvoir, VA, 1986. Lewis Heights NCO family housing quarters.