Answer to "Why is the screen not working?"if your phone fall down and you notice the screen is not working or there is a deletion on it you would have two cases. One, you first have to know that there are two type of screen in any device outer and inner screen. Therefore, if there is a scratch on the screen that means it is the outer screen so consider replacing it. Next, if there is no scratch but the screen is just not working then there is a big chance that the inner screen is damaged. Hence, no need for replacement so just go for new phone because replacing the inner screen would cost a lot near to the price of a new device so buying a new one would be the better idea.
Answer to "Why the battery is not charging up?"if the light of the charging is on while the device is plugged in but still not working then the try to replace the charger and plug it again and see. in case you replace the charger but the still device is not charging up then the chance is it might be the battery therefore replace the battery immediately.
Answer to "Why the keyboard is not responding on my phone?"in case the keyboard is delaying to respond then there is a potential of a frozen motherboard. Therefore, if the motherboard is frozen it would be really simply to fix. All you need to do is to turn the device off for a few minutes and turn it on again. However, if after the device on the keyboard still hanging, then it could be chance that the motherboard is damaged. Therefore, it would be a better idea to buy a new phone becaseu the motherboard is basically to the whole thing in a device and it will cost a lot comparing the device itself.