Wanted: Grammarian to help with cases

[babyignoramus]

Just discovered this board, now I need the help of a pedant!

I've been teaching myself German for a couple of years, and this has involved me going back to square one and teaching myself English Grammar all over again as German is such a minefield.

My question is this - if German has four cases, and other languages (eg. Latin) have more, do some cases come under the umbrella of others? For example, Latin has the locative case - does this fall within the dative case of German?

Can someone point me to a resource which explains every case and what it refers to in simple English? Or some sort of diagram which shows what cases are subdivided into further, more specific cases? Or have I misunderstood this completely and utterly...?????

With my heartfelt thanks in advance!

[Bink]

I'm very fond of Wikipedia, so here's its relevant page (which, charmingly appropriately for here, is tagged with "having multiple 'issues'" ie raises furies of violent challenge in grammatically pedantical bosoms)