Description to correct

My cellphone has   is 5 inches long so it's quite big. It's silver and very modern. To protect it has a transparent cover. It has a 12MP camera and a  though the frontal   front camera not so good. My mobile phone is quite thick and heavy but it is still practical.

Hiiiii!

Hello everyone, I'm Ngoc, I come  from VietNam. I'm 19 years old and I'm studying architecture I wanna want to learn English but I don't know how where to start. I want to would like to improve grammar, vocabulary, listening and speaking skills ... Hope you can help me :<
Thank you! :x

(Hey Ngoc. Good work)

Today, I learned how to write formal letter.

Hello everyone. How are you? 
Today, I learned how to write formal letter from  on YouTube. I think it's very useful. I'm writing for practicing practice and sharing knowledge I'm   I have learned. There are 4 point we need to pay attention to:
1. First, we should not use contraction on a formal letter, such as: don't, can't, shouldn't, and so on...
2. Second, it's not good to use idiom on a formal letter.
3. Third, we should limit phrasal verbs. There are a lot of phrasal verbs in English, it's one of hardest parts for of learning English, and it is not really polite when used on a formal letter.
4. Last, we should not use imperative on a formal letter. It's not suitable if we use imperative for writing to a boss, client or stranger...

I hope sharing this will be useful to you. Please feel free to correct my notebook if I have some mistakes.
Thank you.

(This is quite well written. Good work!)