Writing prompt: My Free Time

Student essay:
My hobby is playing basketball,swimming and so on.But in my free time,I often play computer games with my brother,we often play SanGuo games.I often watch TV and fly a kite.I usually go to the library to buy some books,I thinks it is good for my studys.My friends usually invite me to his party.I have a good time in the partty.I'm very happy,I like my free time.

Corrected essay:
My hobby is playing basketball, swimming and so on. But in my free time, I often play computer games with my brother. We often play SanGuo games. I often watch TV and fly a kite. I usually go to the library to buy some books. I think it is good for my studies. My friends usually invite me to their party. I have a good time in the party. I'm very happy. I like my free time.

Error analysis:
error_sentence: But in my free time,I often play computer games with my brother,we often play SanGuo games.
correct_sentence: But in my free time, I often play computer games with my brother. We often play SanGuo games.
error: ,we
correction: . We
error_type: Punctuation Error
error_severity: 2
error_description: ① Punctuation Error: 〈But in my free time,I often play computer games with my brother〉 and 〈we often play SanGuo games〉 contain independent predicate structures and can be independent sentences, therefore 〈,we〉 is changed to 『. We』; ② Space Error: According to English writing conventions, a space should be kept between a punctuation mark (comma or period) and the following word, so a space needs to be added and changed to 『. We』.
error_sentence: I usually go to the library to buy some books,I thinks it is good for my studys.
correct_sentence: I usually go to the library to buy some books. I think it is good for my studies.
error: ,I thinks
correction: . I think
error_type: Subject-Verb Agreement Error
error_severity: 3
error_description: ① Punctuation Error: 〈I usually go to the library to buy some books〉 and 〈I thinks it is good for my studys〉 contain independent predicate structures and can be independent sentences, therefore 〈,〉 is changed to 『.』; ② Space Error: According to English writing conventions, a space should be kept between a punctuation mark (comma or period) and the following word, so a space needs to be added and changed to 『. I』; ③ Subject-Verb Agreement Error: The subject 〈I〉 requires the predicate verb to be in its base form, therefore 〈thinks〉 is changed to 『think』 to conform to subject-verb agreement rules.
error_sentence: I usually go to the library to buy some books,I thinks it is good for my studys.
correct_sentence: I think it is good for my studies.
error: studys
correction: studies
error_type: Spelling Error
error_severity: 2
error_description: Spelling Error: According to the meaning of the sentence, it is intended to express “studies” here, so 〈studys〉 is a misspelling of 『studies』, and 〈studys〉 needs to be changed to 『studies』 to make the sentence coherent.
error_sentence: My friends usually invite me to his party.
correct_sentence: My friends usually invite me to their party.
error: his
correction: their
error_type: Pronoun Error
error_severity: 3
error_description: Pronoun Error: The subject 〈My friends〉 is plural, and the possessive pronoun needs to be in plural form, therefore 〈his〉 is changed to 『their』 to conform to grammatical rules.
error_sentence: I have a good time in the partty. I'm very happy,I like my free time.
correct_sentence: I have a good time in the party. I'm very happy.
error: partty.I'm
correction: party. I'm
error_type: Spelling Error
error_severity: 2
error_description: ① Spelling Error: According to the meaning of the sentence, it is intended to express “party” here, so 〈partty〉 is a misspelling of 『party』, and 〈partty〉 needs to be changed to 『party』 to make the sentence coherent; ② Space Error: According to English writing conventions, words must be separated by spaces. In this sentence, 『party』 and 〈I'm〉 are two different words and need to be separated by a space, the correct form is 『party. I'm』.
error_sentence: I'm very happy,I like my free time.
correct_sentence: I'm very happy.
error: ,
correction: .
error_type: Punctuation Error
error_severity: 2
error_description: ① Punctuation Error: 〈I'm very happy〉 and 〈I like my free time〉 contain independent predicate structures and can be independent sentences, therefore 〈,〉 is changed to 『.』; ② Space Error: According to English writing conventions, a space should be kept between a punctuation mark (comma or period) and the following word, so a space needs to be added and changed to 『. I』.