My battery dies after only a few hours of use, much faster than when I first got the phone. How can I improve this?

After dropping my phone, half of the screen turned black, leaving me unable to see the top half of the display.

When I answer the phone, I can't hear the person on the other line, even though the screen says the call is connected.

It depends on what is causing your battery problems. If it's the charger itself, you may want to check the connection between the charger and the phone, or replace the charger all together. Another cause of short battery life is an improperly functioning battery. Batteries, especially on older phones, weaken over time. Replacing the battery may get you the extended use you want.

There's no easy fix for this, so you'll need to replace the screen. This can be done by taking the phone apart from the back. See the repair guide for assistance.

You may simply be in an area with poor reception. Sometimes calls can still go through, but the poor reception obstructs your ability to hear the person on the other line. If you're sure you are in an area of good reception, the speaker in your phone may be damaged. If so, you'll want to replace the speaker.