The bottom part of my screen is not responding to touch at all.

First, what phone is it? Troubleshooting steps might differ from each model. If possible, please provide phone make/model for better answers. You would also need the phone model for purchasing replacement parts.

Secondly, most (or all) Android phones are fixable, if you can source the parts. It seems like the digitizer (touch screen) has been broken, probably from an impact that broke some of the fragile electronics. If there are no other damage, you can replace the display entirely (LCD (or else) and digitizer) or digitizer only on supported models.