All of their good reviews on TrustPilot seem to come from people who've posted just one review (which makes me very suspicious). The other reviews suggest that it's a company well worth avoiding!
https://uk.trustpilot.com/review/gunush.com
The reviews on their own website are definitely not to be trusted. Everyone who's submitted a review seems to be delighted with their purchases and, invariably, has appended photographs. (Just how many people do that when reviewing a product, I wonder?). It's probably unsurprising then that the reviews are all so good!
Clicking through to the Apple app store to take a look at the app that's possibly meant to go with the watch seems to show it to be related to discount shopping and actually unrelated at all to the functioning of the watch:
https://apps.apple.com/us/app/gunush/id1538458022