I don't think I have the qualifications to inspire others.

To speak fluent English is my only goal to join you.

To join you is a bit vague here, do you mean to meet in person or do you meet to join this person via your online correspondences.

For example: My only goal for our email correspondences is to improve my English ability. (but I wouldn't recommend saying this too because it sounds like learning English is the only reason you're talking to her lol)

Every person can be excellent, as long as they want to, although there is a lot of hard work they need to giveput in.

Thank you for your praisethe compliment.

"Thank you for the praise." is okay, but not as natural.

I don't think I have the qualifications to inspire others.

To speak fluent English is my only goal to join you.

"to join you" doesn't make sense in context.

Every person can be excellent, as long as they want to, although there iit requires a lot of hard work they need to give.

To be more concise: "Every person can be excellent as long as they have the desire and commitment to work hard."