Learn English – the difference between transplant and transplantation when they are used as noun

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 phrase "[...] their systems' security posture [...]" uses a possessive form to show that security posture quality belongs to the systems.

The phrase "[...] their systems security posture [...]" is using "systems security posture" as a noun phrase, as though "systems security posture" is a thing. This might be a matter of jargon, but I've not heard that expression before. Still, it almost certainly means the exact same thing as the first phrase.