Don’t worry, if you were offered to upgrade, then you correctly reserved it. You just need to help Microsoft to apply it. This guide helps only with one particular issue, it will not help wit others.
You need to check Update History and check information of update. You should see that error code (details) indicates 80240020, if so then this guide will help you.
1. Navigate to location provided bellow and delete everything. Don’t worry it safe, this folder contains Windows update information, including corrupted Windows 10 update.
2. Launch command line as administrator and type this command:
Extra information: you might not be able to delete files requested, if that happens reboot or install “Unlocker” which will show you what is blocking deletion.
While update went smoothly I have some issues which are already all over the internet, main one is video drivers and SLI mode.