Letter to a British Friend

This is one part of PET exam, on this part you have to write a letter in answer to a British friend. In this case, he told me everything about her favorite subjects in school and she asks me what are my favorite subjects, why, and what would I like to study in the future. This was my answer:

Dear Emma:
Thanks for your letter! How are things? I hope you are very well. I´m writing to you because I would like to tell you everything about chemistry and biology and explain to you why they are my favorite subjects!.
Chemistry teaches learns to you about how are the atoms, the periodic table and characteristics of elements. Afterwards, you will learn how are the reactions between molecules occur. There are two main types of mainly parts on chemistry: inorganic and organic chemistry. Organic chemistry is focused on shows the Carbon reactions between carbon molecules in particulary. It is fascinating!
Biology is the other subject that I love it! It is a the life science, isn´t it? You can learn about a lot of things: environment, biochemistry, body human metabolism, molecular biology (this part includes DNA, RNA, genetics and other fascinating things).
In the future, my dream is to become study medicine. Particulary, Specifically, I would like to specialize in oncology and treat patients with cancer!.
I look forward to hearing from you soon!
Love, Jorge.

Letter to a British Friend

This is one part of the PET exam, on this part you have to write a letter in answer to a British friend. In this case, he she told me everything about her favourite subjects in school and she asks me what are my favourite subjects, why, and what would I like to study in the future. This was my answer:

Dear Emma:
Thanks for your letter! How are things (maybe say "how are things now?" as she has just written to you and you are replying)? I hope you are very well (same again here "I hope you are still very well", it isn't wrong it's just the context is a bit weird). I´m writing to you because I would like to tell you everything about chemistry and biology, and explain to you why they are my favourite subjects!.
Chemistry learns to teaches you how are the about atoms,  the periodic table and the characteristics properties ("properties" instead of "characteristics" is more scientific language here, but both are correct English) of the elements. Afterwards, When you go more deeply into the subject you will learn how the molecules react with each other are the reactions between molecules. There are two mainly main parts on of chemistry: Inorganic and Organic Chemistry. Organic Chemistry shows studies the Carbon reactions in particulary particular. This is fascinating!
Biology is the other subject that I love I love it! It's the life´s science, isn´t it? You can learn about a lot of things: environment, biochemistry, body human metabolism, molecular biology (this part includes DNA, RNA, genetic and other fascinating things).
In the future, my dream is to become study medicine (or "my dream is to study medicine and become a doctor"). Particularly, I would like to specialize in oncology and treat patients with cancer!.
I look forward to hearing from you soon!
Love, Jorge.

Good!