A まで means "till A." The A in "A まで B" is the description of the change that coincides or causes the end of B. The A, therefore, is usually a verb of the "change" kind. The verb in A is always in the present tense and in the affirmative.
I will no go back to my country, till I become fluent in Japanese.
When the subject of A is different from the subject of B, the former is marked with the particle が rather than は.
I will sing a lullaby till the baby falls asleep.
You can use "A まで B" in the sentence describing a situation in the past. Note that the verb in A is in the present tense nonetheless.
It was tough untill I got used to Japan.