The Swedish 'sj'-sound (a 'windy' sound) has a a lot of different possible spelling kombination: sj, sk, skj, stj, ch, sch. The A after this 'sch'-sound, is just an untstressed vowel, and yes, A is always called 'hard', because it is a back-vowel, even though it is unstressed.
So if I go to Stockholm and Göteborg speaking the "sk"s with "sh"s people won't find it laughable? Portuguese is my native language, I speak english, I am learning german and swedish, and once I even tried to learn russian, but I got to be honest, I had never found a sound in these languages that I couldn't pronounce even very slowly... until I find this swedish "sk" sound! XD XD XD
I learned recently that "mens" (människa på nederlandska) cannot be used in Dutch always like it can in German to refer to a person and in some cases just sounds wrong. Is that the same case with Swedish, or can I ALWAYS refer to a person as en människa? For example, den tyska människan? Or would that be the German human?
Well, mens in Swedish means period, as in the kind women have, which may be useful to know. About människa, it's a bit complex I think. We use person somewhat less than they do in English. In Russian, they talk a lot about 'the Russian human' in a way that is not natural in Swedish (when discussing how Russian people act and think). Like in your example, it's not grammatically wrong to say den tyska människan, but we rarely use that construction. It's more natural to say either something like den tyska killen/tjejen or tysken/tyskan if you're speaking about one specific person, or, if you're speaking about Germans in general, use the plural tyskar instead.
As an interjection, Människa! works pretty much the same as Mensch! in German. Suitable when you're upset.
Another interesting thing about människa, which I'm not sure we're teaching in the course, is that it is one of the extremely few words (maybe the only one left) which can be said to still have feminine gender, in the sense that if you ever need a pronoun for människan, it should be hon. Authentic example: Herr talman! Så länge människan har funnits här på jorden har hon förorenat. 'Mr President, for as long as mankind has been here on earth, he has been polluting.'
In some dialects, en människa is only used to refer to a female person.
tl;dr You cannot always refer to a person as en människa in Swedish, sometimes it will sound odd.
I don't fully understand what you mean with "cannot be used in Dutch always". It is somewhat context depended, but it's the preferred Dutch word to translate the English word "person". A kind person, I would definitely translate to "een goed mens" or "een aardig mens". "Een aardige persoon" does not sound as natural, though it's not wrong.
In general it's better to say "mens" then "persoon" in Dutch.