Can you "Unrealistic demands"? yes I can, Here you go.

The steps I follow for changing the background are :
-> Take a suitable background.
-> First of all, change the luminosity of the subject. Setting the right luminosity is half the work trust me.
-> Edit the curves a bit to bring some environment color into the subject
-> The do some "trad secret steps". :P
-> Apply a final filter of your liking to both the subject and the background to blend them real goooood.
-> Share it on dribble to get some love reacts.