I have a question on my previous post.

Why do you say "in the morning I usually have a shower/On the following morning/night I had a shower?
I included a few more doubts. Thank you very much.

1)What are you going to do for/during/on (not “in”) your summer holiday?
2) We are going to spend the first day in New York. During the other days we are going to stay near the Niagara Falls (better: We are going to spend the rest of our holiday near the N.F.)
In August I’m going to visit Norway for a week.
3) I’m going to go on a cruise along the Norwegian fiords. We are going to visit the capital city Oslo and other big cities like Bergen, Flan and many others.
4) I’m going to fly from Malpensa airport in Milan to Copenhagen and from there start /go on a trip.
5) I’m going to go sightseeing in Oslo. In particular, I’m going to visit the place where the Nobel prize ceremony is held. My trip is going to last a week.
6) I’m going to return to Milan by plane./I’m flying back to Milan on 2 August in the morning (also: in the morning of 2 August?).
7)I’m going to go on holiday from 19 July to 21 July. My family and I are planning what to do for our next summer holiday.

Why do you say "in the morning I usually have a shower/On the following morning/night I had a shower? I know it's confusing, and I don't have an answer. It's just habit -- idiomatic expressions. http://www.answers.com/topic/idiom

1)What are you going to do for/during/on (not “in”) your summer holiday? I'd use "during" or "for" but not "in" or "on."

2) We are going to spend the first day in New York, and then we are going to spend the rest of our holiday near Niagara Falls.
In August I’m going to visit Norway for a week.

3) I’m going on a cruise along the Norwegian fiords. We are going to visit the capital city of Oslo and other big cities, such as Bergen, Flan, and many others.
"going to go" = redundant; just "going" is usually all you need.

4) I’m going to fly from Malpensa airport in Milan to Copenhagen and from there, I'll leaveon a trip.

5) I’m going sightseeing in Oslo. In particular, I’m going to visit the place where the Nobel Prize ceremony is held. My trip is going to last a week.

6) I’m flying back to Milan in the morning on August 2nd.

7)I’m going on holiday from 19 July to 21 July. My family and I are planning what to do for our next summer holiday.

I will try to answer your questions and explain the reasons for the language choices in your previous post.

1) "What are you going to do for/during/on (not 'in') your summer holiday?"
- When talking about future plans, we usually use the preposition "for" to indicate the purpose or intention. So, "What are you going to do for your summer holiday?" would be appropriate. The preposition "during" is used to indicate a period of time, so you could also say "What are you going to do during your summer holiday?" In this context, "in" is not the most appropriate choice.

2) "We are going to spend the first day in New York. During the other days we are going to stay near the Niagara Falls (better: We are going to spend the rest of our holiday near the N.F.)"
- "In" is used to indicate a specific location or place. So, it is correct to say "We are going to spend the first day in New York." However, when talking about a period of time instead of a specific location, we usually use "during." So, it would be more accurate to say "During the other days we are going to stay near the Niagara Falls." Your suggestion of "We are going to spend the rest of our holiday near the N.F." is also a good alternative.

3) "I’m going to go on a cruise along the Norwegian fiords. We are going to visit the capital city Oslo and other big cities like Bergen, Flan, and many others."
- This sentence is grammatically correct. However, the correct spelling is "fjords" instead of "fiords." Other than that, there are no issues with this sentence.

4) "I’m going to fly from Malpensa airport in Milan to Copenhagen and from there start/go on a trip."
- This sentence is clear and grammatically correct. The use of "start" or "go on" is interchangeable in this context.

5) "I’m going to go sightseeing in Oslo. In particular, I’m going to visit the place where the Nobel prize ceremony is held. My trip is going to last a week."
- This sentence is clear and grammatically correct. The use of "in particular" is a good way to specify your intention to visit a specific place.

6) "I’m going to return to Milan by plane./I’m flying back to Milan on 2 August in the morning (also: in the morning of 2 August?)."
- Both sentences are correct. You can say "I'm going to return to Milan by plane" or "I'm flying back to Milan." Additionally, you can say "in the morning of 2 August" or "on 2 August in the morning" interchangeably.

7) "I’m going on holiday from 19 July to 21 July. My family and I are planning what to do for our next summer holiday."
- This sentence is clear and grammatically correct. The use of "for" indicates the purpose or intention of planning activities for the next summer holiday.

I hope this explanation helps clarify your doubts. If you have any further questions, please feel free to ask!