Manipulating Images

These are the 4 images that i have manipulated with the help of Photoshop. I changed the backgrounds of every image. In some images the changes are a bit more subtle that another.
In the first picture i have made the subject's opacity to the minimum and the background is more prominent in the picture. In the second picture i have tried to merge the image of the girl sitting and the forest together. In the third picture i think it is quite evident the changes that i have made. In the last picture i have placed the on a different background, i have added another picture of space to the sleeves of the subject. I have made the background blur so you can see the subject more clearly.