{table=head] case | masculine | neuter | feminine | plural
Nom | - | - | - | -
Acc | - | - | - | -
Gen | -(e)s | -(e)s | - | -
Dat | -(e) | -(e) | - | -(n) [/table]
{table=head] case | III | IV
Nom | - | -
Acc | -(e)n | -(e)n
Gen | -(e)n | - (e)ns
Dat | -(e)n | -(e)n [/table]
You can see that the declensions have very much begun to collapse. Gender in German, as Yora said, has almost no information to it. The good news is that you've nearly gotten rid of it, if I understood my guidebooks right and put these tables together correctly. In the nouns themselves, masculine and neuter are basically identical in form (with Class III and IV being outliers), feminine nouns are effectively not a thing, and plurals are all collapsed to one set rather than different plurals for each gender.
Weak nouns in modern German don't even warrant a table - they all take -n or -en except in the nominative and they're (almost?) all masculine. Where Old English saw a collapsing system there, German has collapsed it almost into nothing. And where Old English had a strong system of nominative declension with various paradigms and some, but not near-total collapse among the strong nouns, German has nearly collapsed gender (and much in the way of case) and is very close to the position of becoming a genderless language. Your demonstrative pronouns sure aren't helping any matters, though. English collapsed them all to
'the', while German's system is still nearly as robust as Old English and even Old High German (fortunately, less robust than OHG).
The last thing I'll share is a link to the
Old High German declension page on Wikipedia, where you can see the complete insanity of how many declensions there were at that stage in the development of German. Take note of the weak declension, to see what German had at a comparable point to the Anglo-Saxon weak declension.