Concerning the use of Präteritum in spoken German: the Perfekt-construction is definitely used more often. It only happens rarely that Präteritum is used. Additionally, it seems that if someone uses Präteritum, he's more likely to be from northern Germany than from mid or south. I was born and raised in Kiel and my friends from Bavaria have remarked me ...
First of all, in German the position of the subject matters less than the position of the verb, because the latter is usually fixed while the former can move almost freely (however, e.g., not in questions). In both of your sentences, the verb is in the second position:
[Dann] geht [er] [ins Wohnzimmer].
[Er] macht [den Fernseher] an.
In a usual statement ...
You learned the usual declension of Nouns (and articles and adjectives). It is usual to teach only this declension in school. When words like Herz do "funny" forms, they are called exceptions.
But the thruth is that some hundred Nouns do a different declension. They are all masculines with the only exception, the neutral Herz.
Their article and the ...
Weak masculine nouns are:
Masculine nouns that end in an unstressed -e:
der Jude, der Löwe, der Erbe.
Nouns of foreign origin that have their accent on the final syllable (-ant, -ast, -ent, -et, -ist, -nom, -oph, -ot, etc.):
der Polizist, der Assistent, der Philosoph, der Despot, der Astronom, der Gymnasiast.
Some one-syllable masculine nouns that ...
Unfortunately @toy doesn't give examples. I suppose he is talking about sentences like
Ich habe da ein schönes Beispiel.
Donnerstag? Da kann ich nicht.
Also mit der Weihnachtsfeier, da weiß ich noch nicht, da muss ich erst mal mit den anderen sprechen.
Da in those sentences is a sort of general anaphoric pronoun meaning
concerning what we ...