Answer:
"If people are doubting how far you can go, go so far that you can't hear them no more" means that if you go so far in life or by success, you will not be able to hear those who are doubting you.
Explanation:
For example:
People may doubt that you can complete all of your assignments and get good grades. When people doubt you, you probably want to prove them wrong. So, if you reach your goal and go way beyond it (if you got those good grades, and went the extra mile and did more classes and things to further benefit your education) you will no longer be able to hear those who have doubted you.
