Ответ:

Dear Katy,

Here I am in Mykonos, Greece. The weather is fantastic. We are having a wonderful time. At the moment, I am lying by the swimming pool with my brother, James. I am sunbathing and James is drinking lemonade. We swim every day. At night, we usually eat at a restaurant and then we dance at one of the fantastic discos on the island. I love it here and I don’t want to leave!

Love,
Sally

Present Simple употреблён для постоянных состояний и регулярно повторяющихся действий, Present Continuous — для действий, происходящих сейчас или в данный период.