My friend is cooking food. I asked her if it's already ready and she said that it's not ready yet. Now I want to know how much time we have to wait until it'll be ready. What are the common ways to ask it?
Assuming my suggestions below are correct, are there more common choices?
1) How long it's going to take until it'll be ready?
2) How much time remain / left until it'll be ready?
Best Answer
In the comments, @FumbleFingers highlighted some changes needed to your examples.
Note that it's -- "it is" -- needs to be inverted to "is it", because it's a question (see more at this article).
More suggestions
You could replace "it" with the food, lunch, or dinner.
To this they may say something like "in 15 minutes". This seems very informal to me.
Again, seems very very informal.
Eat is fine. Notice that the verb "dine" isn't used this way in conversational English.