I forgot to include the following questions for you to check. Thank you very much.

7) The interviewee got together with two friends of him and they dressed up like a seventies pop group in Afro wigs and dark glasses.
8) His girlfriend had also arranged for a musician to come and play a lot of sevienties music.
9) It was good of her (can you say that?) to put some disposable cameras on the tables so they all his friends could take their photos.
10) She also had them developed so that they could all get copies of the ones they liked.
11) The interviewee had a photo of himself and his friends enlarged and framed.
12) He made a lot of friends including a nice girl that he has seen quite a lot since then (?).
13) As he had broken up with his girlfriend a couple of weeks,Charlie's party really cheered him up.

7 -- delete "of him" -- comma after "friends"

8 -- watch spelling --> "seventies"

9 -- "of her" is fine; delete "they"

10 -- clarify the pronouns -- who are "they" and "them"

11 -- fine

12 -- "girl whom"

13 -- delete "As" and insert "Because" -- add "ago" after "a couple of weeks" -- add a space after that comma

Sure, here are the explanations for each of the questions:

7) The interviewee got together with two friends of his and they dressed up like a seventies pop group in Afro wigs and dark glasses.
To check if the sentence is correct, we need to ensure that the subject and verb agreement is correct. In this sentence, the subject is "The interviewee" and the verb is "got together." They match in terms of number, so the sentence is grammatically correct.

8) His girlfriend had also arranged for a musician to come and play a lot of seventies music.
To check the sentence, we need to determine if the verb tense is appropriate. In this sentence, the verb "had arranged" is in the past perfect tense. It indicates that the action of arranging the musician occurred before some past point in time. The use of "had" implies that the arranging happened before something else in the past. Without further context, we cannot determine if it is accurate.

9) It was good of her (can you say that?) to put some disposable cameras on the tables so they all his friends could take their photos.
To check the sentence, we need to address the use of "it was good of her." This phrase is grammatically correct and commonly used to express gratitude or appreciation for someone's actions. So, the sentence is acceptable.

10) She also had them developed so that they could all get copies of the ones they liked.
To check this sentence, we need to confirm if the verb tense and pronouns are accurate. In this case, "had them developed" refers to the action of getting the disposable cameras' photos processed. The use of "them" refers to the photos. The sentence is grammatically correct and conveys that she arranged for the photos to be developed for everyone to receive copies.

11) The interviewee had a photo of himself and his friends enlarged and framed.
To check the sentence, we need to ensure the verb tense and object usage are correct. In this case, "had a photo enlarged and framed" is in the past tense and describes the action of getting a photo enlarged and put in a frame. The sentence is grammatically correct.

12) He made a lot of friends, including a nice girl that he has seen quite a lot since then (?).
To check the sentence, we need to determine if the verb tense and pronoun usage is appropriate. In this case, "made" is the past tense of "make," indicating that he formed friendships. However, the phrase "he has seen quite a lot since then" is in present perfect tense and seems strange in context. It would be more accurate to use the past tense ("he had seen") to match the rest of the sentence.

13) As he had broken up with his girlfriend a couple of weeks ago, Charlie's party really cheered him up.
To check this sentence, we need to ensure that the verb tense and sentence structure are accurate. In this case, "had broken up" is in past perfect tense, indicating that the breakup occurred before some past event (Charlie's party). The sentence is grammatically correct.