Learn English – the opposite of the perfect aspect

I don't think "present simple" or "past simple" contradict the "adjective noun" ordering rule;

You can consider "present" and "past" (the two morphologically distinct tense forms of the English tense system) as qualifying grammatical aspects (progressive or perfect).
Hence "past simple" or "present continuous".

But it is more a usage than a strict grammatical rule here:
Present simple can also be referred as "Simple Present".

To rephrase the first part (about adjectives) a bit more clearly:

The English Grammatical aspect Wikipedia entry mentions:
"The English tense-aspect system has two tenses, present and past, which are morphologically distinct."

My point is that the tenses act as qualifier (like adjectives do) for the grammatical aspects (same wikipedia entry: aspects beings "simple", "progressive", "perfect", ...).

So if the tenses are considered as adjectives, they are rightly placed in front of the aspects they qualify.

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)