Can you please check these sentences, please? Thank you very much!

1) She told me that it was the second time since she hadn't been to the cinema.
2) She asked me how long I had been waiting for her.
I think you should try to convince his parents that Bill is a trustworthy and responsible boy.
3) You should also tell them that you didn't know he was coming to your house. Tell them that you are attracted by him and you are not going to give him up (?).
4) I'd like to invite you to a surprise birthday party I'm organizing for my boyfriend. I'm going to invite all his old school friends. You are kindly invited to dress up so that he won't be able to recongize you.I'm going to play music from the sixties an have you all dance and sing.
I really hope you can come to my party.

1) She told me that it was the second time since she hadn't been to the cinema.

This doesn't make sense to me. Do you mean "... it has been two months since she's been to the cinema"?

2) OK

3) You should also tell them that you didn't know he was coming to your house. Tell them that you are attracted to him and you are not going to give up his friendship.

4) I'd like to invite you to a surprise birthday party I'm organizing for my boyfriend. I'm going to invite all his old school friends. You are invited to dress up so that he won't be able to recognize you. I'm going to play music from the sixties and have you all dance and sing.
I really hope you can come to my party.

Certainly! Here are the suggested corrections for each sentence:

1) She told me that it was the second time she hadn't been to the cinema since.
- The correct sentence structure should include "she" before "hadn't been".

2) She asked me how long I had been waiting for her.
- This sentence is correct as it is.

I think you should try to convince his parents that Bill is a trustworthy and responsible boy.
3) You should also tell them that you didn't know he was coming to your house. Tell them that you are attracted to him and you are not going to give him up.
- The phrase "Tell them that you are attracted by him" can be changed to "Tell them that you are attracted to him".
- Additionally, the phrase "and have you all dance and sing" is missing punctuation. It should be "and have you all dance and sing."

4) I'd like to invite you to a surprise birthday party I'm organizing for my boyfriend. I'm going to invite all his old school friends. You are kindly invited to dress up so that he won't be able to recognize you. I'm going to play music from the sixties and have you all dance and sing.
- The phrase "recongize you" should be corrected to "recognize you".
- The sentence "I really hope you can come to my party" is missing punctuation. It should be "I really hope you can come to my party."

Overall, here are the corrected sentences:
1) She told me that it was the second time she hadn't been to the cinema since.
2) She asked me how long I had been waiting for her.
3) You should also tell them that you didn't know he was coming to your house. Tell them that you are attracted to him and you are not going to give him up.
4) I'd like to invite you to a surprise birthday party I'm organizing for my boyfriend. I'm going to invite all his old school friends. You are kindly invited to dress up so that he won't be able to recognize you. I'm going to play music from the sixties and have you all dance and sing.
I really hope you can come to my party.

Please note that grammar and sentence construction can vary based on the desired writing style and context.