The First Day on italki

In titles, the first letter of most words are capitalized. italki is not capitalized because the company chooses to use all lowercase letters. When we talk about using electronic devices and things such as phones, applications, websites, computers, and the internet, we use "on".

Ex. I'm online. Stop playing on your phone.

Hello, my name is Nhi, but I chose the English name Rebecca.

"my" is not starting the sentence. Adding "but" shows contrast. Your birth name/given name may be Nhi, but you go by Rebecca.

I'm from Vietnam and I am learning English.

Perfect :)

I hope to have many friends and learn English better.

"many" means "a lot". It has to be used with plural nouns. "a lot" can also refer to amounts so it can be used with either singular or plural nouns.

Ex. I have many friends. They write many paragraphs in their practice journals each day. There are a lot of cats in that room. We have a lot of food right now. I love you a lot.

Nice to meet you. (It's nice to meet you.)

The My first day in at  italki

Hello, My name is Nhi, I chose the English name Rebecca.
I'm from Vietnam and I am learning English. I hope to have many friends and learn   improve my English better.
Nice to meet you.

Nice to meet you too Rebecca, welcome to Italki ! :-)

The first day in italki

Hello, My name is Nhi, I chose the English name Rebecca.
I'm from Vietnam and I am learning English. I hope to have many friends and learn english better.
Nice to meet you.

Nice to meet you, Nhi!