1文目: [意見(Yes/Noで聞かれたら質問を繰り返して答える)]. I have two reasons.
※語数オーバーする場合は「I have two reasons.」を省略してもOK
2文目: First, [理由1].
3文目: Second, [理由2].
I like summer better. I have two reasons. First, I like swimming in the sea with my friends. Second, we have a long vacation in summer, so I can go on a trip.