If the tablet has been in contact with water or any other sticky liquid, the buttons may stick when pressed. the best way to resolve this issue would be to tear the device apart using the preliminary guide. wipe down the buttons with 90% isopropyl alcohol and let them dry for 24-48 hours. After this step is complete, you can reassemble your device and hopefully the issue will be resolved.
Broken glass or a faulty connection between the digitizer and motherboard may be the issue to your problem. The digitizer is responsible for converting the touch commands to the digital image. If your device's screen is malfunctioning, it would be best to follow the screen and digitizer replacement guide on this device's main page.
If the tablet has been used and recharged constantly for a long period of time, the resilience and ability for the battery to retain charge is probably low. This is a problem that all lithium-ion batteries face, and it can ultimately be solved by outfitting the device with a new battery.