This is a difficult area of English for foreign learners, and I’m afraid you’re not going to understand it fully from a few answers here. Very briefly, you use the present perfect continuous form to talk about events in the recent past, particularly activities that have not been completed. The form is often found with the prepositions ‘for’ and ‘since’, as in ‘He’s been speaking for a very long time’ or ‘I’ve been working non-stop since this morning’.
Here are a few examples contrasting the present perfect with the present perfect continuous:
'I’ve done my homework' (it’s finished) / 'I’ve been doing my homework' (it’s not finished)
‘I’ve drunk my coffee' (it’s all gone) / ‘I’ve been drinking my coffee’ (there’s some left)
‘It’s rained every day since the weekend’ (repeated rain) / ‘It’s been raining all day’ (continuous rain)
Your own examples don’t really illustrate the use very well. You wouldn’t say ‘I have learned English language in the past few weeks’, because that suggests you’ve finished your studies and you don’t need to do any more. That’s unrealistic. No one learns English in a few weeks. I think these two examples might show the difference more clearly:
‘I have been studying English for two years’ (I’m still studying it)
'I have studied English, but I don’t speak it very well' (I studied it at some time in the past, but am not studying it any more)
The big difference here is active and passive voice. The original sentence is in active voice. In your suggested options, I think you're trying to use passive voice, but you need to change the order of the words.
When you say “it should be opened,” it is the object of the opening. But the object should be the window. So you want to say “One new popup window should be opened.” Note that in passive voice, you don't say who or what is doing the opening.
The same goes for the message: “the following message should be displayed.” Again, you don't say that the window is doing the displaying.
Putting it together, you could say:
One new popup window should be opened and the following message should be displayed to the user: “Thanks for your feedback.”
Note that you could use active voice for one part and passive for the other, though that is probably more awkward.
Generally, the choice of voice is determined by the style guide, or consistency with the rest of the document. So check whether someone has made a guide for these documents and if not, just pick either active or passive voice and use it throughout.
Best Answer
Both:
are correct.
Note should be taken of the fact that with definite determiners (in this case "your") the preposition "of" will be preferred, while with an indefinite determiner (in this case "a") the preposition "for" can be used. It should also be taken into account that "of" is much more usual than "for", which will only be accepted in restricted contexts such as (2) above.
According to Seth Lindstromberg in English Prepositions Explained, while "of" expresses referential possession (the word has a definition) or a verb-object relationship (the word is defined), "for" expresses purpose (I want a definition for the purpose of defining this word).
Something similar can happen with other nouns, for example "solution":
Here is a good reply concerning the degree of idiomaticity of "a solution for" as compared with "a solution to" (in answer to to Ram Pillai's comment below).