Photoshop - General Comments

Well, sometimes it's hard to correct yourself especially when you are not that familiar with the subject, in my case, photoshop. But for example regarding this photo:

Many students and some lecturers told me that the dress came over exposed to the background,  and I came out of proportion. This is the first photo I ever did with Photoshop at school during the lecture. I really appreciate everyone's comments because actually I learn from my mistakes like anyone else. Originally it was something like this :

Then for example this photo,

The combination of the background with the dress and the earrings came perfect but unfortunately for the hair it is obvious that it did not came natural and so if I could try and do it again I would leave the natural hair as it originally was right here :

Thanks. Feel free to leave comments as I would read each single comment and take good attention to every opinion you suggest. That is how we learn! Goodnight.