Problem Matching Watch with IPhone and WatchOS update

I have not used Apple Watch before. I have just brought an Apple Watch Series 3. I started matching with my iPhone XS with iOS 12.4installed. However, my Watch App on the iPhone is now keep saying installing the WatchOS 5 for more than two hours!!! The Apple Watch seems ok, and is waiting to match with the iPhone...

if i try to cancel the WatchOS update, the iPhone warns me that it will return to the factory setting. I don’t know what to do... should I wait and should I cancel the update and restart everything again?