Answer:
Hey Anna,
yesterday was Olivia's ten birthday.
Olivia is my sister.
She was so happy about her birthday.
After breakfast I told my sister that she must went with me.
When we came in the "Secret place" Olivia was confused.
Someone went lights out. Her friends from school, parents, grandparents and cousins came with big pink lego cake and sang birthday song. Olivia started cry because she was surprised. Her friends bought her small lego house with farm but our parents bought her big lego house. She was happy. She got good gifts from everyone. All night we sang, jumped, played and ate. It was really great time.
I can't wait to see you, write me.
With love, your best friend.