Let's say the cooking time for a dish is 50 minutes. I want to ask how much time remains between now and when the dish will be done.
What is the right way to ask that?
When will the dish be ready?
After how much time will the dish be ready?
***Not a native speaker.***
How much time is left until the (dish) is ready?
There are other ways to say it, but this is pretty general.
I think these two examples will do it for you:
How long before it's ready?
How much longer before it's ready?
You could go about it a couple of ways. One would be to straight up ask what you basically already said:
How much time remains for [insert action/activity/etc. here]?
Or you could say something along these lines:
How much longer will this take?
You could (if you wanted) replace "this" with whatever thing you're asking about.
How much longer will the dish be cooking?