Windows are notoriously bad at stopping noise. Window salesmen can also be notorius for selling you windows that do not help stop noise either. They know less than what you have already learned about noise and how to stop it. Here is what we know.
If you have outside noise getting inside and you have windows -- those will be your main problem. They are typically so bad, that until you fix your windows, you will not have quiet. Under standard construction methods acceptable in the USA today, the walls stop a lot of noise, doors stop a good amount and windows stop very little.
Whether you have the older single pane windows or the newer dual pane windows, you can do more to stop the noise.
Continue to Soundproofing and Window Pane Thickness.