The course must provide a written transcript for every single piece of audio or video content. If you watch a lecture or a dialogue, you must be able to read exactly what was said. This allows you to "spot the gap"—discovering that what you thought you heard is different from what was actually said.
Here is the secret that most separate apps and courses miss: course english fluency reading listening
A leverages this synergy. You aren't just learning words; you are learning how the words feel when spoken and how they look on the page simultaneously. The course must provide a written transcript for