I'm quite new to this. I want to become very Articulate able to express myself when it comes to uspeaking English. I'm quite new to this. I want to be able to express myself when it comes to using English.

I'm quite new to this . I want to become very Aarticulate when it comes to speakingith English. I'm quite new to this. I want to become very articulate with English.

We don't capitalize the first letter of a simple adjective like "articulate". We'd only capitalize an adjective if it's a nationality or is part of a name or title. "when it comes to ________ing" isn't wrong, but I'm more likely to use it when introducing someone who has (or doesn't have) a very special talent: "I'm not that great when it comes to cooking", or "When it comes to speaking English, Jonathon is quite articulate!" Here, you could also say "I want to become very good at speaking English". However, after an adjective like "articulate", I would say "with". I'm more likely to say "with" if the adjective already has something to do with the action or noun after it (English is a language, and "articulate" means "good at speaking and using a language, usually English"). However, both are fine in most situations.

I'm quite new to this . I want to become very Aarticulate when it comes to speaking English. I'm quite new to this. I want to become very articulate when it comes to speaking English.

* I disagree with other people correcting "when it comes to speaking English". It is perfectly fine, no corrections needed.