Why is my battery life draining fast once I updated to Android Oreo

[Android Central Question]

On 3rd May 2018 I have updated my Lenovo K8 Note of its third update since August 2017. After this update the device battery is draining terribly fast and getting hot during charging and internet surfing. Also the the operating system is not so user friendly.

 

[belodion]

What is using the charge, in Settings, Battery?