> I went to the pension when winter vacation starts. I went there with some friends family.
At there we ate delicious food. It was meat, kimbab, rice, live octopus. I ate live octopus for the first time in my life.
There was a swimming pool there. We played in there for a long time at the first day and at the second day morning. I went to the swimming pool. The swimming pool was inside the building.
Correction: Student's sentence Corrected sentence Grammar explanation Better
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I went to the pension when winter vacation starts.
I went to a pension house when the winter vacation started.
To indicate that the action or event is already finished, use the past tense of the verb "start" which is "started"
At there we ate delicious food. It was meat, kimbab, rice, live octopus. I ate live octopus for the first time in my life.
We ate delicious food like meat, kimbab, and rice there. It was also the first time I ate a live octopus in my life.
There was a swimming pool there. We played in there for a long time at the first day and at the second day morning. I went to the swimming pool. The swimming pool was inside the building.
There was a swimming pool inside the building. We spent a lot of time in the morning playing there during our first and second day.
You can use during instead on "at" in this sentence. "During" is a preposition that means from the beginning to the end of a particular period