Rules don't prepare you for a native speaker who talks at full speed, drops the idioms, and assumes you'll keep up.

That's exactly what your Cambly tutor does, because that is their English.                
                
They bring the culture, the current references, and the way things are really said.

Lesson by lesson, you stop translating in your head. You start thinking in English instead.               
                
Summer is when schedules open up.
When there's finally space for something that actually moves the needle.