wish and hope both express the emotional attitude of the speaker- a desire for something. wish can have overtones of sadness or disappointment- you expect not to get something, whereas hope expresses optimism- you do expect to get something, usually with reason.
can and could both indicate the real situation, or the speaker's rational assessment of it. can is used about something that is possible: could is used about that is improbable.
Using the combinations hope/can and wish/could reinforces the message.
I hope I can visit all the countries in the world one day.
This expresses an optimistic desire to visit all countries, backed up by a rational belief that this will be possible.
I wish I could visit all countries in the world.
This expresses sadness: a longing to do something that the speaker rationally considers to be impossible. Note that, because the speaker considers it impossible, they would not finish it off with one day.
To address your question: these are two standard forms that carry the right emotional and rational overtones for most situations, but neither really fits the bill for your situation. If you could combine hope with could, this might convey the right meaning, but this combination is never used about future events. You will therefore have to spell out exactly what your emotional and rational additude is:
I hope to visit all the countries in the world one day, but I know that it's going to be difficult.
I'd never really thought about this one before now - but this mixing of 'so' and 'very' is very much a non-native 'tell'. Natives do it without thinking, of course, so when a non-native has to choose which to use, it's very noticeable to a native if they choose the wrong one.
So, how to pick which one?
This is the conclusion I came to...
You can use 'so' to mean 'very' but not always.
In a simple statement it works well.
Oh, this food is so good.
But in a lot of cases there is some element of comparison, which 'very' doesn't have.
Think of 'so' as having some kind of limit, some quantity or quality which is unstated but has a kind of invisible count.
I like it so ||||| much.
I don't like it so ||||| much, I only like it this ||| much...
That's not so ||||| much as if I liked it very (|||||||___) much.
'Very' doesn't have this 'count' or 'grade' hint to it, it's just 'a lot'.
I thought their last album was very good, but this one is not so good.
'So' in this last case has an 'invisible count' of whatever 'very' had just before, but failed to match up to that count.
Their last album was very good but this one is so much better.
Again, we've somehow quantified an uncountable 'very', put a value on it & made 'so' more than that.
Even if there's no value to compare to except ... life itself...
I don't like this sandwich so much
that's really comparing it to all the other sandwiches you've ever had, putting a value on them, then measuring it against your current sandwich's 'score'.
Best Answer
Definition
The definition you referred to is Oxford Learners Dictionaries: congratulation: "1 congratulations [plural] a message congratulating somebody (= saying that you are happy about their good luck or success)."
"Congratulations" comes after the success is achieved, and you are saying that you observed their success or good luck and approve of it.
"Good luck" must come before their success - you are saying you hope they will succeed.
Congratulations and good luck!
You could congratulate someone for taking a prestigious exam, such as a bar exam, especially if the person was expressing a positive sentiment at the fact that they had finally reached this point:
Jane: "Hey Joe, guess what!"
Joe: "What!"
Jane: "I'm almost finished! Tomorrow I'm sitting for the bar exam!"
Joe: "Congratulations!"
(You might also say "Congratulations! And good luck!")
"Taking an exam" vs. "doing an exam"
While "I'm taking an exam" is much more common, there are other phrases that are acceptable or even preferred within certain dialects of English. Note the following Google N-Gram:
Some of these results have a different context, such as a doctor who says, "I'm doing an exam" is performing an exam on someone. However, there are instances of "doing an exam" referring to the same meaning as "taking an exam" within the exact same idiomatic scenario. (There are also some subtle cases in different scenarios that could influence usage.) It would be conservative to use the phrase "I'm taking an exam" unless the culture you're in uses a different idiomatic phrase.
Credit to @Adam and other commenters for ideas and content of this answer.