For the first picture I attempted to adjust some of the color to make it look more like real life. This picture stated a little darker at first. After I adjusted it you could see the sky was lighter.
In this tree picture I attempted to get rid of the bright white light behind the tree. I also attempted to bring out the trees color and lighten up the tree trunk to make the tree stand out.
The city lights picture I attempted to make the city lights pop out a little more. I made the image darker while increasing the contrast and decreasing the shadows.