When my father walked with me to the train station, I saw many seagulls flying over the Hai River. It reminded me that when I was in middle school, I would* sit by the Hai River with my classmate, drinking beer and watching seagulls during the lunch break. At that time, there were not so many seagulls in our city, so they were very new to us. We talked about what they were. Normally, we called them seagulls, but it was a river. My friend said: "Then they must be river gulls." When I was young, there was a very popular Korean drama called "Autumn in My Heart." The protagonist said that if she had another life, she wanted to be a tree, so she would not be separated from anything around her. If a tree had feelings, it would not have been so lush and green. *Using the simple past tense is fine, however, I've changed it to 'would', which can mean 'used to'. When 'would' is used in this way it represents a habitual action in the past. As you are talking about a past, reoccurring action, 'would sit' works very well in this case.

"When my father walked me to the train station, I saw many seagulls flying over the Hai River. It reminded me of when I was in middle school, sitting by the river with my classmate, drinking beer and watching seagulls during our lunch break. At that time, there weren’t many seagulls in our city, so they felt new to us. We talked about what they were. We usually called them seagulls, but since it was a river, she joked, 'Then they must be river gulls.'" "When I was young, there was a very popular Korean drama called "Autumn in My Heart". The protagonist said that if she had another life, she would want to be a tree so that she would never be separated from the things around her." "If trees had feelings, they wouldn’t be so lush and green."