Question

Please check my new copy:

I believe the essential qualities a leader must possess are to set a vision and to be able to lead. A leader must be able to set a vision to seek for improvement and change the mistakes. A leader must be able to set a vision for improvement to make things better.A leader must be able to lead in order for his/her group to agree and reach the group's goal. If a leader can't lead, effects are that goals wouldn't be reached.

Answer 1

You have written "set a vision" three times. And there are other problems in here.

1. Go through and delete ALL repeated ideas.

2. Clarify what you mean by "must be able to lead" -- you still haven't said what that means.

Revise.