Couple of tips: when you take a photo in game, choose the option to share it. It'll upload it to the Forza servers and you can download it either from the website or the Forza Hub app. If you do that you won't have the '[Esc] Back' in the bottom right corner.
For free hosting sites, Flickr is usually recommended around here because it's basically the best one, but for alternatives you can use photobucket (pretty good but have been known to wash out colours with their compression techniques in the past) or even just use imgur.
As for your photos, they're a nice start! You'd get a sharper image with a shorter shutter speed, and the highlights in a couple of the night shots are a bit blown out - taking photos at night is much trickier to get a natural lighting. I really like the composition of the second shot, and the first and fifth shots really convey the action nicely.