Imaam forgetting ayat and changing surah

Assalam-o-Alikum wa rehmatullahi wabarakatuhu

Mufti A.H Saheb i want to ask you one question about the Jammat Namaz :

Actually one day i am performing Jummah Namaz with Jamat on that time Imam sahab Forgets the Ayat then after few seconds of silence he changed the Surah and the Completion of Jamat he can’t Perform “Sijda Sahu” so i want to ask you is my Jummah Performed or i have to perform Qaza ? secondly i want to ask one more thing Mufti Saheb can we have permission to Remind the Ayat Loudly when imam Forgets the Ayat in Qirat or he does any mistake in ayat on that time when we are in jamat ?