Can you please tell me if the following sentences are possible?

I really don't know how to say it in English. Thank you.

1) I do the shopping at the market every Saturday. (Should I consider it a mistake if the sentence started with "every Saturday"?)
2) I'm tanned because I spent a week at the seaside.
3) When I was young,I used to pimples on my face. Now I'm starting having wrinkles on my forehead.
3) I stayed at the seaside for a week/I spent a week at the seaside./I was at the seaside for my holidays (are they all possible?)
4) I became a member of the local football club last June. I'm a mid-fielder.
5) I like riding my bike/cycling/car-racing (are they all possible)
6) I took out a membership (or I became a member of ) to the local swimming pool. OR I bought a membership card to use the swimming pool for a month.
7) When you join a football club, you are given a membership card.
8) I enrolled in a ballet course.
9) During my summer holidays I relaxed a lot. (?)

1 and 2 are correct. You could start the sentence with "every Saturday."

3. I used to have pimples . . .
4. All are good.
5. I like riding my bike. I like cycling. I like car-racing.
The rest of the sentences are fine.

1) The sentence "I do the shopping at the market every Saturday" is grammatically correct. Starting the sentence with "every Saturday" is not a mistake, as it specifies the frequency of the activity.

2) The sentence "I'm tanned because I spent a week at the seaside" is also grammatically correct. It explains the reason for having a tan due to spending time at the seaside.

3) The sentence "When I was young, I used to have pimples on my face. Now I'm starting to have wrinkles on my forehead" is grammatically correct. It describes a change in appearance over time.

4) The sentences "I stayed at the seaside for a week," "I spent a week at the seaside," and "I was at the seaside for my holidays" are all grammatically correct. They describe different ways of expressing spending time at the seaside.

5) The sentences "I like riding my bike," "I like cycling," and "I like car-racing" are all grammatically correct. They describe different activities that the person enjoys.

6) The sentences "I took out a membership to the local swimming pool" and "I became a member of the local swimming pool" are both grammatically correct. They describe becoming a member of the swimming pool. The sentence "I bought a membership card to use the swimming pool for a month" is also grammatically correct, but it specifically mentions purchasing a membership card for a limited period.

7) The sentence "When you join a football club, you are given a membership card" is grammatically correct. It explains that when someone joins a football club, they receive a membership card.

8) The sentence "I enrolled in a ballet course" is grammatically correct. It states that the person registered or signed up for a ballet course.

9) The sentence "During my summer holidays, I relaxed a lot" is grammatically correct. It describes the person's activity of relaxing during their summer break.