"Ja, danke, Mann."
Can this one be interpreted in the same way as it is in English, "Yeah thanks man"? Basically can "Mann" be used for "dude", "mate", "buddy" etc as well as to mean plain old "the man"?
Thanks! Yes it's the colloquial meaning that I wanted to check! (Sometimes Duolingo seems to throw together words a bit for the sake of a sentence, at least at this basic level when I know only a few words).
I have heard of the word 'alter' being used for 'dude'. Can anybody confirm if this is true?
Yes, but it's very slangy. If you want to sound like a 13 year old street kid – possibly with immigration background, 'Hey Alter, was geht?' is your choice.
Me as a german native speaker, I never used "Ja, danke, Mann" only "Ja, bitte" as accepting an offer or "Danke, Mann" for thanking, but you can also use "Danke".
Why isn't "Yes, thank, man" correct? The verb is in the first person, so it should work. So why the 's'?
This reminds me of a common mistake my Polish students make. They always say 'Thanks God' instead of 'Thank God,' which is what native English speakers say. We are essentially saying something like:
A I found my wallet. B (You should) Thank God.
I don't think it is. "danke" is short for "ich danke dir/euch/Ihnen" ("I thank you"). So a literal translation of "danke" would be the first person singular form of the verb, i.e. "thank" in English, as dexez said. But a literal translation, as is often the case, doesn't make sense. So we replace it with something an English speaker would actually say, like "thanks" (or "thank you").