Learn How to Downgrade
If you absolutely hate Android 8.0 Oreo's features and/or performance, you should be able to downgrade back to Nougat.
We recommend getting familiar with the downgrade process before the Android Oreo update arrives. This way you'll be prepared.
Downgrading from Android Oreo to another version of Android will take time, particularly for those of you new to the process.
If you don't know how downgrading works on Samsung phones, this guide from XDA-Developers will help point you in the right direction ahead of Android 8.0's release.