Photoshop 6 and Layers

Hello guys I'm new to Photoshop and have a question about making 2 different
pictures in 1 image. So what I did I took 1 background picture from the
first picture. Got another person from the second picture and got second
person from the third picture. I put it everything in one picture.
Everything looks fine except it doesn't look real. Background and one
person looks nice and the other person doesn't look real. It looks like I
put the person on purpose. What I mean by this is one person with
background looks real and the other person looks much closer. I've tried to
use Blur feature but it doesn't help can anybody help me just give me a few
tips how can I make the whole image look like real one so no one can say I
put those people on purpose.

Thanks,

Almazick

Yeah, turning a few pictures into one seamless, realistic picture can be trouble for anybody.

I suggest fooling with image/adjust/hue/saturation controls on the two people, to get them too look similar in saturation. One may be too brightly colored compared to the other.

Keep fooling with those filters. I suggest adding some noise to the layers and see if you can get a similar "graininess" to each of them. Don't just try using them, if you can find a good combination of blur, sharpening, and noise, that may be your best bet.

You also could be falling victim to the two people having two entirely different light sources when the picture was taken of them. That would also look unnatural. Fixing that would be a tougher thing to do, but could be done with steady work with an airbrush and clone stamp tools.