Thank you very much for all.

Here are some more sentences I'm not sure of.

1) My family is made up of/composed of/formed by three people: my father, my mother and I (or me?)
2) My family consists of three people.
In my family there are three people.
3) I like riding my motorbike (but: going for a ride on my motorbike)
I have a twin sister called Jessica
I have a little dog and I'm in charge of feeding it.
4) In August I was on holiday with my family in the mountains.
I went to a small mountain village called Pieve.
5) When I returned home, there was the annual village festival. A cattle fair was held for the occasion where farmers took their animals.
6) I helped waiting at table.
7) How do you call the meeting organized at the beginning of the school year when the parents get to know the teachers?
How much/high was the half-board price?
8) I went to see the performance organized by the hotel entertainers.
9) I spent the rest of my stay (?) there sunbathing.
10) I regretted coming back home.
11) I wished I could stay there longer.

Now, now, now ... you're slipping back into the bad habit of posting everything instead of only the ones you REALLY are unsure of.

Pick 4 or 5.

1) All three options - "made up of," "composed of," and "formed by" - are correct to describe the composition of your family. However, it would be more appropriate to say "My family is made up of/composed of/formed by three people: my father, my mother, and me" (using "me" instead of "I").

2) "My family consists of three people" and "In my family, there are three people" are both correct ways to express the idea that your family has three members.

3) "I like riding my motorbike" is a correct sentence to express your enjoyment of riding your motorbike. However, it would be more accurate to say "going for a ride on my motorbike" instead of "riding my motorbike" when referring to the specific act of going for a ride.

- "I have a twin sister called Jessica" is a correct statement to introduce your twin sister.
- "I have a little dog and I'm in charge of feeding it" is a correct sentence to express that you have a dog and you are responsible for its feeding.

4) "In August, I was on holiday with my family in the mountains" is a correct sentence to describe a vacation trip you had with your family during August.
- "I went to a small mountain village called Pieve" is a correct sentence to mention your visit to a specific mountain village.

5) "When I returned home, there was the annual village festival. A cattle fair was held for the occasion where farmers took their animals" is a correct description of an event that took place in your village.

6) "I helped waiting at the table" is correct to describe your role in assisting with serving tables or waiting on customers.

7) The meeting organized at the beginning of the school year where parents get to know the teachers is commonly referred to as a "parent-teacher meeting" or a "back-to-school night."

- To ask about the price of half-board, you can say "How much was the half-board price?" or "What was the cost of half-board?"

8) "I went to see the performance organized by the hotel entertainers" is a correct sentence to describe attending a performance arranged by the entertainment staff at the hotel.

9) "I spent the rest of my stay" or "I spent the remaining time there" would be more appropriate phrases to convey your intention of sunbathing during the rest of your stay.

10) "I regretted coming back home" is a correct sentence to express your feeling of disappointment after returning home.

11) "I wished I could stay there longer" is a correct sentence to express your desire to extend your stay in a particular place.