1) You need to watch out for cropping off the top of the head, also his face is lit on the sides and not the center if he turned a bit towards either side it would help, there is also a soft focus or slight motion blur, and looks like you are pushing the usable ISO limits of your camera.
2) Here too you are pushing the ISO, but I like the lighting on the guys face (but here too it looks soft in the focus) but the girl's face is mostly just noise with light on the hand, you could try and up the contrast or burn it slightly and turn her more into a silhouette which could add some nice mystery into the photo.
3) You have a slight motion blur on one of the hands, and a bit tight crop on the side. As a composition it doesn't speak to me so much in it;s composition but as a moment in your life.
4) You have a lot here, including some background, try focusing on a single element of the bike. You don't need to go extreme (I do
) but bring the viewer into an element or with your shot a landscape for the background could work.
5) I'd try some different angles but the color and idea has lots of promise, I would try to get a more dynamic "portrait" of the tree outside.