+1 as the same problem I had! You spoke my words ;) But here, my daughter is 8 (and this problem still persists though it has become less frequent now!).
Okay, the problem of crying. Young ones often get disappointed or frustrated if the things don't work their way. On the other hand, it's not possible for parents to fulfill every wish they wish!
The first issue you told in your question is you don't understand her question. There, the solution is try to ask her and understand what she wants. If possible, give her what she wants and that's the only thing to deal with child's psychology. They are not mature enough to understand the finer nuance what we try to explain them.
The second thing you said is because she wants something right now. The only thing that works there is distract her mind (that's what I practiced!) by taking her out or asking to play some game or whatever she likes the most (we know what our kids like...right?). Meanwhile, ask someone in your house (say your wife) to arrange for that thing that she wants right now. Again, do this if that thing is possible. If she asks for the moon, we are just helpless ;)
The tendency of crying frequently is seen in many kids (and I'm a healthcare provider with experience in pediatrics). And the only solution there is the time, the maturity that comes naturally. When they grow older, this tendency goes. However, if the frequency is getting increased, we shouldn't take it lightly as in some rare cases, this tendency grows as stubbornness and from there, it takes the victim to the next level of depression.
What has worked in my case is whenever Rhyme (my daughter) cried for a trivial thing, I distracted her mind showing something that'll surprise her. At the age of five, they certainly understand our language and I'd always tell her that okay, what she wants will happen now...but see this....and then distraction. If they cry hard, on the other hand they forget soon (Thank God!). After that surprise element, the thing that she was crying for, in most of the cases, is forgotten. We can then tackle them the way we want.
Once she grows, tell her the value of crying and inform her that frequent crying will lose its value (this has worked as surefire in my case). "If you cry seldom, everybody'll be bothered that something big must have happened to you but then if you cry on trivial matters, how would we know that it's something very serious you are crying for." But of course, this matter she'll understand when she is nearly 8.
All the best and I hope she's back to her happiness and does not cry frequently. :)
A very good read is here.