Chosen Solution

I just bought an Iphone, sadly when I open the box, I got a phone with aftermarket screen and loose button (specially the home button, clicking unlike common iphone. Question here is: Can I fix the button insted of replacing it? And how much oem screen of iPhone?

If you have any recourse with the seller, I would send it back or open a dispute (eBay?). They clearly sent you a defective phone when you were expecting a working one. Does the iPhone allow you to register any fingerprints (TouchID)? If so, then you have the original button and it cannot be replaced without losing this function. It may just be that the whoever replaced the screen didn’t do a good job of transferring the Home Button, nor changing the gasket. Take a look at this guide if you want to open up your phone. You can get a good quality screen here.

Return and file chargeback on your credit card!