Database

db={"quizResults":[{"_id":ObjectId("6118fa0ac4bc55c37ef95536"),"questionId":ObjectId("611632305bd3910929b95542"),"vidId":8225342,"viewerId":"00420185-ec25-44de-beb7-a7b3a17cc867","__v":0,"answerId":ObjectId("611632305bd3910929b95544"),"isCorrect":true,"quizId":ObjectId("611632305bd3910929b95541"),"whenAnswered":ISODate("2021-08-15T11:27:21.975Z")},{"_id":ObjectId("6118fa0ac4bd55c37ef95536"),"questionId":ObjectId("611632305bd3910929b95542"),"vidId":8225342,"viewerId":"00420185-ec25-44de-beb7-a7b3a17cc867","__v":0,"answerId":ObjectId("611632305bd3910929b95544"),"isCorrect":true,"quizId":ObjectId("611632305bd3910929b95541"),"whenAnswered":ISODate("2021-08-15T11:27:21.975Z")},{"_id":ObjectId("6118fa24c4bc55c37ef98cc1"),"questionId":ObjectId("611632305bd3910929b95546"),"vidId":8225342,"viewerId":"00420185-ec25-44de-beb7-a7b3a17cc867","__v":0,"answerId":ObjectId("611632305bd3910929b95548"),"isCorrect":true,"quizId":ObjectId("611632305bd3910929b95541"),"whenAnswered":ISODate("2021-08-15T11:27:32.100Z")},{"_id":ObjectId("6118fa2bc4bc55c37ef98e94"),"questionId":ObjectId("611632305bd3910929b9554a"),"vidId":8225342,"viewerId":"00420185-ec25-44de-beb7-a7b3a17cc867","__v":0,"answerId":ObjectId("611632305bd3910929b9554d"),"isCorrect":true,"quizId":ObjectId("611632305bd3910929b95541"),"whenAnswered":ISODate("2021-08-15T11:27:39.965Z")},{"_id":ObjectId("6118fa31c4bc55c37ef9906d"),"questionId":ObjectId("611632305bd3910929b9554e"),"vidId":8225342,"viewerId":"00420185-ec25-44de-beb7-a7b3a17cc867","__v":0,"answerId":ObjectId("611632305bd3910929b95551"),"isCorrect":true,"quizId":ObjectId("611632305bd3910929b95541"),"whenAnswered":ISODate("2021-08-15T11:27:45.221Z")},{"_id":ObjectId("6118fa36c4bc55c37ef991a3"),"questionId":ObjectId("611632305bd3910929b95552"),"vidId":8225342,"viewerId":"00420185-ec25-44de-beb7-a7b3a17cc867","__v":0,"answerId":ObjectId("611632305bd3910929b95553"),"isCorrect":true,"quizId":ObjectId("611632305bd3910929b95541"),"whenAnswered":ISODate("2021-08-15T11:27:50.734Z")}],"quiz":[{"_id":ObjectId("611632305bd3910929b95541"),"status":2,"vidId":8225342,"questions":[{"_id":ObjectId("611632305bd3910929b95542"),"questionNum":1,"questionName":"What value has the number PI?","answers":[{"answerId":"61bcf6fa-745b-47d8-8d4d-9b7f1806cca0","answerType":0,"_id":ObjectId("611632305bd3910929b95543"),"answerName":"3.12","isCorrect":false,"hotspotId":469988,"overlayId":null,"panelId":""},{"answerId":"94eef1e2-a783-4e5d-944f-942de24b8bed","answerType":0,"_id":ObjectId("611632305bd3910929b95544"),"answerName":"3.14","isCorrect":true,"hotspotId":469987,"overlayId":null,"panelId":""},{"answerId":"ea642211-a458-4c72-89d6-60ae99140ec0","answerType":0,"_id":ObjectId("611632305bd3910929b95545"),"answerName":"3.16","isCorrect":false,"hotspotId":469986,"overlayId":null,"panelId":""}]},{"_id":ObjectId("611632305bd3910929b95546"),"questionNum":2,"questionName":"When the World War 1 Began?","answers":[{"answerId":"7fa63324-31a7-447f-bfe7-0923bdbf2df0","answerType":0,"_id":ObjectId("611632305bd3910929b95547"),"answerName":"1912","isCorrect":false,"hotspotId":469993,"overlayId":3,"panelId":"12abc"},{"answerId":"32c541f0-1bc6-483b-aca9-92bf4a027303","answerType":0,"_id":ObjectId("611632305bd3910929b95548"),"answerName":"1914","isCorrect":true,"hotspotId":469989,"overlayId":4,"panelId":"12345abc"},{"answerId":"0bd3cb57-0bd8-40a6-bfbe-3bcc8482833f","answerType":0,"_id":ObjectId("611632305bd3910929b95549"),"answerName":"1918","isCorrect":false,"hotspotId":469986,"overlayId":3,"panelId":"12abc"}]},{"_id":ObjectId("611632305bd3910929b9554a"),"questionNum":3,"questionName":"At the end of which century William Shakespere wrote the work of halmet?","answers":[{"answerId":"64325f3c-37ee-42c7-8d1e-bad5004999f4","answerType":0,"_id":ObjectId("611632305bd3910929b9554b"),"answerName":"XIV","isCorrect":false,"hotspotId":469994,"overlayId":3,"panelId":"12abc"},{"answerId":"139630bf-06da-49c0-8066-bd983b8659af","answerType":0,"_id":ObjectId("611632305bd3910929b9554c"),"answerName":"XV","isCorrect":false,"hotspotId":469995,"overlayId":4,"panelId":"12345abc"},{"answerId":"d324ec8c-6abc-434d-b7d9-a3837752919b","answerType":0,"_id":ObjectId("611632305bd3910929b9554d"),"answerName":"XVI","isCorrect":true,"hotspotId":469992,"overlayId":3,"panelId":"12abc"}]},{"_id":ObjectId("611632305bd3910929b9554e"),"questionNum":4,"questionName":"On which Island is the Mount Tied located?","answers":[{"answerId":"65a1db58-7038-4713-b378-6faf6c98a7a0","answerType":0,"_id":ObjectId("611632305bd3910929b9554f"),"answerName":"Martinique","isCorrect":false,"hotspotId":469996,"overlayId":3,"panelId":"12abc"},{"answerId":"6c16ee3b-5bcc-497b-a250-8f169a510142","answerType":0,"_id":ObjectId("611632305bd3910929b95550"),"answerName":"Cabrera","isCorrect":false,"hotspotId":469997,"overlayId":4,"panelId":"12345abc"},{"answerId":"2d035092-76cf-46ca-bea4-15b0c1654306","answerType":0,"_id":ObjectId("611632305bd3910929b95551"),"answerName":"Tenerife","isCorrect":true,"hotspotId":469998,"overlayId":3,"panelId":"12abc"}]},{"_id":ObjectId("611632305bd3910929b95552"),"questionNum":5,"questionName":"Which is the best selling record in history?","answers":[{"answerId":"078f441b-373f-40e9-89e1-04fca0a9fc5d","answerType":0,"_id":ObjectId("611632305bd3910929b95553"),"answerName":"Thriller Michel Jackson","isCorrect":true,"hotspotId":470114,"overlayId":3,"panelId":"12abc"},{"answerId":"644b80fe-5778-46fa-b3a6-1eff5989cdee","answerType":0,"_id":ObjectId("611632305bd3910929b95554"),"answerName":"A kind of Magic Queen","isCorrect":false,"hotspotId":470113,"overlayId":4,"panelId":"12345abc"},{"answerId":"5bde2682-66fe-4c79-a728-aea67f6842a8","answerType":0,"_id":ObjectId("611632305bd3910929b95555"),"answerName":"help The Beatles","isCorrect":false,"hotspotId":470112,"overlayId":3,"panelId":"12abc"}]}],"__v":0}]}

Query

db.quiz.aggregate([{$match:{"vidId":8225342}},{$lookup:{from:"quizResults",pipeline:[{$match:{"vidId":8225342}},{$group:{_id:"$answerId",count:{$sum:1}}}],as:"quizResults"}},{$project:{_id:1,questions:{$map:{input:"$questions",as:"q",in:{_id:"$$q._id",questionName:"$$q.questionName",questionNum:"$$q.questionNum",answers:{$map:{input:"$$q.answers",as:"a",in:{$mergeObjects:["$$a",{$let:{vars:{fst:{$first:{$filter:{input:"$quizResults",cond:{$eq:["$$this._id","$$a._id"]}}}}},in:{numResponses:"$$fst.count"}}}]}}}}}}}}])

Result