battery drains fast because it updates in background or some app like what's app use battery and data in background if you block this apps battery doesn't drains fast
Going to need a lot more info than that if anyone is going to help. You can try gsam battery monitor app which is free in play store... it will help you to get further details regarding your situation.
Hi and Welcome to AC!! Another factor is your data signal. The lower signal means that phone is constantly looking for a signal and will use battery. I agree try Gsam battery monitor that is a helpful tool in finding out if an app is a culprit. If you would like additional help please let us know what phone and OS you have