1. How is he slow as a turtle? No one caught him from behind at that counter when he passed to Semedo. He runs fine. Tottenham players are turtles too?
2. All players tire fast in the first game of the preseason tour. It's why you do a preseason tour in the first place. To adjust the fitness level of the players.
3. When 3-4 opponents caught him he passed backwards because the players around him didn't give him a better alternative. He is not a player who is scared to make a pass if one opens up to him. This will be the job of the players around him.
Let me say this:
If you say that 4 opponents caught him, it means 3 Barca players were left unmarked (or were loosely marked at best) as a result of their markers pressuring Arthur. Those unmarked players need to do something to get on the ball. Basically move around and make gestures so they can be spotted by the ball carriers. You always saw the likes of Alves making gestures like that he was open and unmarked. Messi does that too. This is exactly what we want. Opponents crowding our skilled players. It means they leave gaps that can be exploited. It's hard to spot unmarked players if they hide behind opponents, or if they don't make themselves available. From ground level the view must be very different and a lot harder to cope with.
Man, literally, nothing makes sense from what you wrote. You're looking for flaws that aren't there in this game. Wait some more.