Can someone help me find the mistakes in the following sentences?

The sentences are short but I want to be sure about the correct use of the prepositions.
Thanks
1. I went skiing with my dad to St Moritz (OR in St Moritz)
2. At Christmas (or On Christmas Day) I ate a lot of sweets
3. I chatted with my friends ON my computer
4. I helped my mum with the housework, for example (?) I cleaned the table and I tidied my bedroom.
5. I played songs with my guitar, which I found ON the web (?)
6. I helped my grandparents with the animals (OR I helped look after my grandparents’ animals?)
7. My Christmas holidays are just finished (OR have just finished)
8. They lasted a week but I feel they flew (??) OR they have just flown by
9. I also spent two days in the mountains with some of my friends (or some friends of mine??)
10. I like the snow very much and I enjoyed skiing a lot (?) and throwing snowballs
11. On Christmas Eve I went to a church to see one of my friends who acted in a performance and after that I stayed for the midnight mass (OR I attended the midnight mass)
12. After the mass I went back home and I exchanged presents with my friends.
13. The most exciting moment was the Christmas Day when I got up early to unwrap the presents that were under the Christmas tree.
14. During my holiday (or holidays?) I went to… I returned home for Christmas, because I wanted to spend it with my family.
15. I spent New Year’s Day with my friends at Paul’s home (OR house?)
16. My holiday finished on……(holiday or holidays?)
17. My uncle prepared a good fish (can you say that?)
18. We exploded or we burst a lot of crackers (?)
19. In the evening I watched TV up to late (or TILL late?) Can you say I usually stayed up late watching TV.
20. I made a lot of Christmas presents but I received a lot , too.
21. On my Christmas holidays (or During ….) I got up late.

Franco,

Please go over these aloud, and then post the ten (no more than ten) that you absolutely have no clue about.

1. in

2. During
6. either
7. have just
8. have just flown
9. either
11. either
13. Christmas Day = drop "the"
14. holidays is a bit better
17. yes
19. till late or the last
20. During

Sra

Sure! I can help you find the mistakes in the sentences and provide explanations for the correct use of prepositions. Here are the corrections and explanations for each sentence:

1. Correction: "I went skiing with my dad in St Moritz."
Explanation: When referring to a specific location, we use the preposition "in" instead of "to."

2. Correction: "On Christmas Day, I ate a lot of sweets."
Explanation: The correct preposition to use when referring to a specific day is "on," not "at."

3. Correction: "I chatted with my friends on my computer."
Explanation: When using a device or platform to communicate, we use the preposition "on."

4. Correction: "I helped my mum with the housework, for example, I cleaned the table and tidied my bedroom."
Explanation: The sentence structure is correct. The only addition is the use of a comma after "for example" to separate it from the rest of the sentence.

5. Correction: "I played songs on my guitar, which I found on the web."
Explanation: When referring to the source or origin of something, we use the preposition "on," such as "on the web."

6. Correction: "I helped my grandparents look after their animals."
Explanation: Both sentences are correct, but combining them to say "I helped my grandparents look after their animals" improves clarity.

7. Correction: "My Christmas holidays have just finished."
Explanation: The correct verb tense to use when describing a recently completed event is the present perfect tense, "have just finished."

8. Correction: "They lasted a week but it feels like they have just flown by."
Explanation: The sentence structure is correct. The change is using the pronoun "it" as the subject of the second part of the sentence, and inserting the word "feels" to express the speaker's perception.

9. Correction: "I also spent two days in the mountains with some friends of mine."
Explanation: Both options are correct, but removing "of mine" while saying "some friends" makes the sentence more concise.

10. Correction: "I like the snow very much and I enjoyed skiing a lot and throwing snowballs."
Explanation: The sentence structure is correct. The only addition is using "and" to connect the activities "skiing" and "throwing snowballs."

11. Correction: "On Christmas Eve, I went to the church to see one of my friends who acted in a performance, and after that, I attended the midnight mass."
Explanation: Both options are correct, but breaking the sentence into two parts with the use of commas improves readability.

12. Correction: "After the mass, I went back home and exchanged presents with my friends."
Explanation: The sentence structure is correct. The addition is using the verb "exchanged" to better convey the action of giving and receiving presents.

13. Correction: "The most exciting moment was Christmas Day when I got up early to unwrap the presents that were under the Christmas tree."
Explanation: The sentence structure is correct. The change is removing unnecessary usage of "the" before "Christmas Day" and adding clarity to the subject of unwrapping presents.

14. Correction: "During my holidays, I went home for Christmas because I wanted to spend it with my family."
Explanation: The correct term to use is "holidays" to refer to a period of time off from work or school.

15. Correction: "I spent New Year's Day at Paul's house with my friends."
Explanation: Both options are correct, but specifying "house" instead of "home" in this context is more specific and accurate.

16. Correction: "My holiday ended on..."
Explanation: The term "holiday" should be used in singular form when referring to a specific period of time off.

17. Correction: "My uncle prepared a good fish."
Explanation: To describe the preparation of a specific type of food, we use the article "a" before the noun, such as "a good fish."

18. Correction: "We burst a lot of crackers."
Explanation: The verb "burst" is more commonly used when referring to fireworks or firecrackers rather than "exploded."

19. Correction: "In the evening, I watched TV until late." OR "I usually stayed up late watching TV."
Explanation: Both options are correct. The change is using "until" instead of "up to" and rephrasing the second sentence to improve clarity.

20. No correction needed. The sentence is correct.

21. Correction: "During my Christmas holidays, I got up late."
Explanation: Both options are correct, but specifying "during" is more accurate when referring to a specific period of time.

I hope this helps! Let me know if you have any further questions.