On summer vacation, I went to Spo1 Park. I went there by car. In the swimming pool of Spo1 Park, I enjoyed swimming and learned how to swim on my back (how to swim the backstroke, how to do the backstroke). It was not easy to swim on the back. I always feel so happy when I look at this picture.

(Would you check the passage? Correct errors,please. And give me some good expressions which I can use, please. Thank you.)

Here's a revision. One thing you can do to make your writing better is to start combining ideas so there aren't so many short sentences.

During summer vacation, I went by car to Spo1 Park. I enjoyed swimming in the pool there and learned how to do the backstroke. It is not easy to swim on my back. I always feel so happy when I look at this picture.