However, Arnautovic's last few matches have been quite good, from possession of the ball today against Atletico he was quite good, it's just that his confidence needs to be improved, if he scores again in the second leg then he will be more confident.
What makes you think he lacks confidence though? He's quite composed and realized he could do better based on his interview. He mentioned his injury and stuff like that so I don't think he's facing some confidence crisis, not to mention his form in the recent matches is quite good as you said[1]. I think he's been doing fine for a 34-year-old who doesn't really have solid game time due to injury etc[1].
[1]
https://www.inter.it/en/news/arnautovic-interview-champions-league-inter-atletico[2]
https://whoscored.com/Players/34693/Show/Marko-ArnautovicI know it is not easy to win against Italian clubs at their home ground, but Atletico Madrid could have done better against Inter Milan yesterday. There is hope for Atletico Madrid to qualify for the next round of the UEFA Champions League if they improve their performance when Inter Milan visits them at home and also defeat them by two goals to nothing.
I mean that's true for almost every match where a team played terribly, especially if they don't create any shot on targets at all. I think this is more of a mental issue IMO, considering how some teams perform well even in an away match. A 1 goal difference is definitely going to impact how the 2nd game will go, I'd be surprised if ATM doesn't play a high-pressing game to score as soon as possible so they can switch the momentum to their side ASAP.