Bridget gets a letter from Argentina, and a new characters will be/come there soon. Bridget gets a letter from Argentina, and a new character will be/come there soon.

"Come" would sound better than "be"

Enjoy watching ! Enjoy watching!

There is never a space between a letter and a comma, full stop or exclamation point.

Enjoy watching ! Enjoy watching!

It is suitable for language learners who possess a beginner level. It is suitable for language learners who possess a beginner level.

Great job using the word suitable. You need a be a bit more specific here.

It is suitable for beginner levelanguage learners. It is suitable for beginner language learners.

It is suitable for beginner levels. It is suitable for beginners.

The characters ofin series are funny. The characters in series are funny.

When speaking about characters in a movie, book, or series we use 'in' not 'of.'

The characters ofin the series are funny. The characters in the series are funny.

The characters of the series are funny. The characters of the series are funny.

You can learn new words and improve listening skills. You can learn new words and improve listening skills.

Instead of “words” you a say, “ vocabulary.”

You can learn new words and improve listening skills (by watching it). You can learn new words and improve listening skills (by watching it).

Nothing wrong with your original sentence, I just suggested adding this to add more flow to your sentences (because you never use 2nd person before this)

This is a story ofe plot centers around Bridget and Annie who share a flat in London. The plot centers around Bridget and Annie who share a flat in London.

This just feels more like it comes from a native speaker. What you wrote was fine but felt like it was a beginner's level.

ThisIt is a story ofabout Bridget and Annie who share a flat in London. It is a story about Bridget and Annie who share a flat in London.

This is athe story of Bridget and Annie, who share a flat in London. This is the story of Bridget and Annie, who share a flat in London.

I have been watching ean English series for two months. I have been watching an English series for two months.

You always capitalize 'English.'

I have been watching ethe English series, “Extra,” for two months. I have been watching the English series, “Extra,” for two months.

I have been watching ean English series for two months. I have been watching an English series for two months.

Have you ever heard of “Extra”? Have you ever heard of “Extra”?

Have you ever heard of “Extra”? Have you ever heard of “Extra”?