不一会儿

Soon, you can say 马上, for example: 等一下，我马上就回来！ Just one second, I will be back soon!

Here 不久 and 很快, their meanings are roughly the same. Both of them mean "after a short time". The reason why you feel confused is because the word "快" has several meanings in Chinese. The general 3 meanings of "快" 1. Fast, quick/quickly (in terms of the speed of movement) e.g. 马跑得很快。 The horse can run very fast. 2. After a short time. In the near future. e.g. 晚饭很快就好了。 The dinner will be ready soon. 3.Happy,delighted. e.g. 我很快乐。 I am happy. Therefore, "很快"can mean both very fast and very soon.

eeh... let me kindly ask you... why are you asking about chinese or why are you wailing to translate so much? I ask you it becase I found you are using so much the dictionary to guess what's the meaning of each word, which is not a very good way to approach to the chinese language. For example, "soon" in enlgish has a meaning but in chinese there are a lot of ways to get the feeling of soon. As Jeff said, 馬上 has a feeling of "immediately" and according with the sentence you can translate it as "soon". Another word can be used for it is "快“ or "近“ or even ”早“ but as far as I know there is not a special word to say "soon". I think the better way of get approached of the language, specially asian languages which are so far from the european languages, is understand the words and the grammar bat itself, by their logic and not translating from the meanings and concepts from ours languages! Hope it didn't sound so mean ^^ is just a kind advice!

grazie..si infatti avevo capito che 马上 significa anche immediatamente..spesso non è facile trovare delle parole equivalenti..ho notato che ci sono parole differenti a seconda della distanza nel tempo..mi interessava una parola per esprimere genericamente "presto", che non sia immediatamente comunque :)