Great game. A free to play game, isometric view.
Kinda like Diablo type games except you have missions and just enter stages from town to clear the stages. Very polished, controls very nicely, all round fluid movements, looks beautiful.
Cash shop offers you a chance to pay to win of course but the chances to acquire good gear in the game without spending money are very good too. So it's not like, if you don't spend money, you don't get to progress further at some point in the game. It's very accessible without paying but will obviously take a lot more grind and is a very good, long-term game for mobile.
No idea if it's on iOS.
The UI in the video is old and the game has since been updated many times so many things may be improved since this video.
Then you just suck at the game. I don't know what else to say. I would say he is moderately difficult even for first encounter. If you fail for the first time then the second one is easy as pie as you know what to expect.