for flu grate an onion very finely and take 2 heaped tablespoons in a cup of weak tea (no sugar and milk) and sip it as hot as possible and get into a warm bed and sleep. You will never take anything else when you have flu, you will feel better in the morning, continue for a few days even after feeling better, the flu won't come back, best flu remedy ever.
Best serious remedy is lots and lots of water it will make your chest mucus thin and easy to cough up keeps you from smothering with phlegm lodged in you windpipe as happens to me without water. Also drink before bedtime a glass of water. Note. Be wary of mean people giving bogus remedies. Unable to breath with phlegm is serious..
Put 2-3 tablespoons of honey (preferably raw) into a small cup (like an espresso cup) warm it up in the microwave for 15 seconds, add cinnamon powder and ginger powder, mix well with a little spoon, add a half of a tablespoon of lime juice and drink up while warm (not hot so it won't burn you). 3-4 of these throughout the day and the congestion is gone.