Why can't I turn the iPhone 5 on?

It was the first time to open my phone. I was going to replace my battery, but when i tried to separate front case, I could not arrange the force and I could not control it. I think the cables between front case and back case got damaged a little bit. Later I replaced the battery and I closed it. But the screen is not working. I plugged the phone to charger it overheats and makes kind of warning sounds in every 2 or 3 second. I checked from itunes it is getting charged but not any sign of light in the screen.