Android Oreo has been in news ever since its release last month. There is an air of excitement amongst the users being able to use Android Oreo as it was only available for Nexus and Pixel devices, but recently other smartphone producers like Motorola, HTC, OnePlus, and Nokia selected devices will also be getting the Android Oreo 8.0 updates. In some cases where updates are not available for the older version of the phone, you can try to download the XDA developers forum for the unofficial ROM.
https://technoidhub.com/android/how-to-remove-app-is-running-in-the-background-notification/2627/