As to why 'deutscher Fußball' is wrong. No idea... as it is actually correct. ;-) At least on its own. In a sentence it may change, e.g. Ich sehe gerne deutschen Fußball.

I don't think it does. People are always speculating whether the grammatical gender discloses some sexist bias but it's important to differentiate between the gender of the words and the "real" gender. Of course, the biggest issue is that the grammatical terms are "masculine", "feminine", "neuter" for the "gender". That drives people especially from an English language background generally crazy who are not used to the concept. Personally I would prefer if there had been different terms maybe - making this up on the fly - this word is "fo", "fa", "fi" (rather than masculine, feminine, neuter). :-) That way people would no long speculate why the table in German is "masculine" but the the cup is "feminine".

That's a great question! There are lots of good German language books around. Of course, it all depends what you're level is right now. Looking at your profile it seems you are still somewhere at the start which means that you're probably restricted in what you understand. As such I would recommend to stick to maybe children's books, e.g. Michael Ende's Jim Knopf or books by Janosch. The last one is also popular with adults. If you want "proper" stories you could try and find "Heftromane", e.g. the series of Jerry Cotton crime stories or the John Sinclair horror novels (not too horrific). These are generally 64 pages, published weekly and written in normal but not too demanding German. (High literature they sure ain't. LOL) The downside: They are usually only on sale in German railway stations and difficult to get outside of Germany. Some, however, may also be available in eFormat. Here e,g, is one that can be ordered to download for free: http://www.thalia.de/shop/ebooks_kostenlos/rubrikartikel/der_hexer_01/wolfgang_hohlbein/ISBN3-8387-2167-5/ID33289131.html Last but not least: Look for "zweisprachige Bücher", i.e. books that are available both in English and German for parallel reading.

"Grüssen" und "begrüssen" sind nicht gleich aber sehr ähnlich. "Grüssen" ist ein kurzes "Hallo" oder auch non-verbal wie z.B. ein Wink von einer Strassenseite zur anderen. "Begrüssen" ist normalerweise ein wenig intensiver und in der Regel nur im direkten Kontakt, also nicht aus der Ferne. Aber die Unterschiede sind oft sehr subtil.

Sie können nicht mehr als Nein zu dir sagen.

Beides sind Sätze und keine Fragen. ;-) "Ich war noch nie in Frankfurt" ist korrekt. Der andere Satz ist nicht ganz richtig. Man kann aber sagen: "Ich bin noch nie in Frankfurt gewesen." oder "Ich bin noch nie nach Frankfurt gefahren." Das Perfekt bei "fahren" oder "sein" wird mit "sein" gebildet (und nicht mit "haben")