If I correctly interpreted what you are asking...
Dear (insert your friends name),
How are you doing? Currently, I am doing quite well. Why, you might be thinking to yourself, well I will tell you. I just recently went on a field trip to the zoo! We went for our French class and it was so much fun. I saw the bird of prey display, I saw a lion, and I got to ride on the train. On the field trip I learnt a lot about animals in French, did you know cat in French is “chat”? I know I sure didn’t! Anyways, it has been a pleasure writing you, but I have to go now.
Sincerely,
(You’re name here)
I really hope this helps!