In the match vs Arsenal, almost all of Man United's problems at the beginning of the season can be slowly overcome and there is progress. The distance between the players is close, the combination of good passing combinations, the fighting power and high energy of each player, the competition between players, the players often press and there is movement without the ball, etc. What is still lacking may be passing accuracy that is not yet high (still average "70-80% only) and games that like to drop in the second half (not as aggressive as the first half)
I don't know what it's like behind the scenes but Ten Hag is quite successful in terms of mentally motivating the players, they even seem to have more passion and positive energy that can be transmitted to other players, especially new players like Martinez and Antony.
Manchester United's success in beating Arsenal cannot be separated from Erik ten Hag's role in choosing the players to be played and reserved in my opinion, even though Arsenal dominated the game as Arsenal usually do in every game.
I watched the game to the end on television and I think there were a few things that made Arsenal lose for the first time this season in the Premier League. Arsenal's defense failed to establish communication with the defensive midfielders in anticipation of Rashford and Eriksen. Marcus Rashford has speed so it is very easy for him to receive a quick pass from Eriksen.