The 18-year-old Greenwood broke the deadlock in the 22nd minute with a cool finish to score his third goal of the season and second in this competition.
The Scotland striker, 29, has been sidelined with a thigh injury, having spent the second half of last term away from football due to mental health issues.
"We needed a win, but we needed a performance".
Frimpong will be making the squad for Sunday's game at the Celtic Park.
We are not looking too far ahead, taking it game by game and we will see where it takes us.More news: Russian Napoleon-expert found drunk in river with student’s severed arms
Celtic icon Bobo Balde has posted on Twitter after his old club produced a stunning display to beat Lazio 2-1 away from home thanks to goals from James Forrest and Olivier Ntcham - who scored the victor in the 95th minute.
The goal came after a counter-attack in the 95th minute when Odsonne Edouard played in Ntcham.
Ghent's 3-1 upset win at VfL Wolfsburg saw the Belgian side go top in Group I, while Espanyol's 6-0 home drubbing of nine-man Ludogorets has them on the cusp of qualifying from Group H. The penultimate round of group games will be played on November 28.
Celtic skipper Scott Brown described the victory as "exceptional".
UEFA also opened disciplinary conditions versus Celtic and Lazio just after lovers traded anti-fascist and fascist gestures during Celtic's two-1 win in Glasgow past month.More news: Inmate Argued His Life Sentence Ended When He Died And Was Revived
The German club moved second in Group J, ahead of Roma on head-to-head and two points behind leaders Istanbul Basaksehir, who saw off 10-man Wolfsberger 3-0 in Austria. "This win was important".
Forster also revealed that Celtic will now be aiming to top their group.
No Celtic team had won in Italy before so it is an awesome achievement and fantastic to qualify out the group already.More news: Kmart in Kenosha to close January of 2020
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