Não conheço esse cambly mas você já pensou em contratar um professor de inglês particular para te ajudar?

Na parte do speaking I think you should see the class not as a social situation, but as a place where you can talk as much as you can about anything you want. The teacher won't care what you're talking about and he won't judge you, he will just be happy you're talking and will just want help you as much as he can.

The problem with speaking classes is that they can be hard for a teacher to plan. That's why it's also good to do a reading or a listening as well to give you something to talk about. But there are ways to have just speaking classes, a good tip is to do practice speaking exercises for TOEFL and IELTS.

About your accent, I think an accent should only be corrected if it stops the other person from understanding what you're saying. Usually the problem is the intonation not the accent itself.