This is the group stage not the knock out stage where away goals count so Basaksehir can score as many goals as they like as long as Manchester United their games they should qualify as winners or runners-up in the group.
Honestly, Manchester United is a failed club, they are losing almost every match they play.
in the past, Man U was one of the best clubs in Europe, now their performance is getting poorer. See as a club called Istanbul beat them 2-1
I dont know if Manchester United is a failed club due their inability to perform well as their fans expected but they only lost some few games in the EPL Cup, Europa etc. Ji However, their today's game against the Istanbul Basaksehir is still a reasonable result since they are away and what need to do in their next game is to make sure their Basaksehir dont score more than 1 goal.