It’s not too late to start anything. As I can see you have a good command of English even now. What you have to do is just to improve it only. I hope you received some good advises from our friends on how to improve your English.
So I’ll give you a Tip, on how to communicate with clients.
If you feel that you don’t understand what your client says, be honest let him/her know that You really like to help him/her but didn’t understand what he said. Use these words:
“I really like to help you but I’m sorry I didn’t understand what you said. Could you explain please?”
He will definitely explain so you get a 2nd chance. With the time you will be more familiar with the language.
Remember language is not a barrier to become a successful person. I’m sure you will overcome this obstacle over the time and be a STAR on fiverr.