An English newspaper is a newspaper made in England, regardless of language; a newspaper in English or an English-language newspaper can be made anywhere in the world, but you'll know even before you read it that it's written in English.
I put the same thing, but immediately realized that it's not quite proper. Although, given context, any english speaker would understand.
The setence refers to Newspaper translated into English and not a newspaper produced in England.
In my class I think they said that dum, duma etc are used in spoken Portuguese but are not written.
I think those contractions are used more freely in European Portuguese. This advice from a Portuguese site: http://www.ciberduvidas.pt/pergunta.php?id=27735 says that they can be used even in formal situations, including academic texts, provided you use them consistently, that is provided you do not use "de um" in one place and "dum" in another.
As far as I know the moderator of the Duolingo lessons doesn't accept them, and I don't think you'll find any sentence using them here (except, perhaps, in the Idioms Bonus Skill).
DL is apparently accepting the dum/num contractions now, at least on some of the exercises I have remembered to try them on, so ironically, not consistently.
"Em" is an uncontracted form (if placed right before a noun group, it means that noun doesn't take the definite article).
"No(s)" and "Na(s) are contractions of "em" with the definite article (o/os; a/as) - it needs to agree with the rest of the elements of the nouns, i.e., it is inflected according to the gender and number of the noun that comes after it.
So when there is no gender or article, or in/on before a Perfect noun, like Inglês in this case, it will just be em. Right? I got that. But why is it "Vejo voce na Monday" instead of "Vejo voce em Monday"?
Because the word you identify as "Monday" - we prefer to call it "segunda-feira" or "segunda" - actually takes the article after "em", all days of the week do.
P.S. There's always going to be "gender" in Portuguese words - every single one of our nouns is either masculine or feminine - what you may not have is the article that marks directly.
There are different opinions regarding the use of the article with proper nouns (which is what I think you meant by "Perfect noun"): I can't go into much detail, but for languages you shouldn't use it when you're talking about an attribute of the language ("something written in English") and not the language itself (English as "the English language").