There's many ways to do this, the simplest is to colour key the green out and just scale your video down to fit in. You can get more complex by adding a subtraction mask, what sort of style are you looking for specifically?
Hi Muhammad Qais,
Are you still facing this problem? If not, let us know how you solved it. If so, please let us know so we can assist you further.
I would recommend to use the keylight effect to key out the green in the TV. The best results are when you set the output to Intermediate Result, instead of Final Result. Maybe this tutorial will help you out:
Hope this helps
If the object with the green screen is moving in the shot you will need to do some tracking. In practice it is almost never necessary or even productive to apply a green screen to a TV set, a phone screen or any similar item that you want to replace in post. Problems include spill light, lack of detail for tracking, and the lack of reference reflections. Absolutely the only advantage that I can see is that it may make it easier to separate things that pass in front of the screen into layers. On the other hand, more than 90% of the roto that I have done on these kinds of shots is extremely simple.
Here's one of a couple dozen techniques that can be used to replace screens, signs, or objects in a shot and match the look and feel of the original shot. I produced this short tutorial from footage supplied by a user to this forum that was facing a similar problem.