This video is speaking
If we get the subway, we will be on time?
and giving this slide
Should I use "we will" or "will we"?
English Language Learners Stack Exchange is a question and answer site for speakers of other languages learning English. It only takes a minute to sign up.Sign up to join this community
You can use either, but the meaning changes.
If you say "will we" you make a question. You are asking another person to predict or give their opinion. The other person could reply "Yes, because the subway is quick" or "No, the subway will take 30 minutes and we only have 10 minutes left."
If you say "we will" you are stating your opinion. It makes a statement and not a question.
Now it is is possible to ask a question by using intonation, but this makes the question biased. Saying "We will?" carries the implication "I think we won't!" It is unlikely to use question intonation to ask a biased question like this with an "if" clause, because that looks like a genuine question and not a biased one.
So in short, if you want to ask a question like this, use proper question grammar, don't depend on intonation.