I had an discussion in English as an activity for my club.

Through the activity, I improved not only my English but also the ability to think and the ability to communicate.

Discussion makes me think about what the correct phrase is.

Is that correct?

Do those who speak English say "confirm"?

No one around me knewhow to knowthe correct phrase.

If you know, would you tell me that?

I had an a discussion in English as an activity of my club. (use "a" if the word after it begins with a consonant. use "an" if the word after it begins with a vowel)

Through the activity, I improved not only my English but also my ability to consider and ability to communicate. (I'm not too sure what you meant about your ability to consider. consider means to take not of something or taking something in to account)

Discussions make me think about what the correct phrase is. (did you mean "Discussions make me think about constructing correct phrases"?)

Is it that correct?

Those Do those who speak English say "confirm"? (depends on the sentence. Confirming is like making sure. So to say "I would like to confirm your idea" may also mean "I would like to make sure about your idea". did you understand? hehehehe)

No one around me knows how to knowuse the correct phrase. (When "No one" is your subject, you add an "s" to the verb related to the subject)

If you knew know about that, would you tell me that?

I had a discussion in English as a(n) activity for my club.