Yes, "am" is short for "an dem". You could also use an indefinite article if you are not talking about a specific Monday: "An einem Montag". When talking about a specific Monday, I think we always use "am" instead of "an dem" unless a relative clause follows that describes that specific day. e.g. "Am Montag gehen wir ins Schwimmbad." "An dem Montag, an dem meine Tochter geboren wurde, war ich sehr glücklich." In the plural form you can skip the article but in most cases it also doesn't sound wrong to use it: "An Tagen ohne Arbeit ist mir langweilig." "An den Tagen ohne Arbeit ist mir langweilig." "An Tagen, die sonnig sind, gehe ich gerne raus." "An den Tagen, die sonnig sind, gehe ich gerne raus." "An den Tagen wie diesen" would sound kinda strange though. But I'm not sure why.

Jemand, der flüstert, hat die Intention leise zu sein. Er versucht trotzdem so zu sprechen, dass sein Gegenüber ihn versteht. Jemand, der murmelt, spricht meist eher unabsichtlich leise und undeutlich.

Wir schreiben 1,00€

Hi Daniel, that's actually a really good question and not very easy to answer. The meaning of "laufen" und "gehen" partly depends on the local dialect. In Austria, 'laufen' means 'to run' or 'to walk fast', whereas 'gehen' just means 'to walk' or 'to go'. It's the same in some parts of Germany. In other parts of Germany the two words are used as synonyms though and just mean 'to walk' while 'gehen' can still also mean 'to go'. So if you say "Ich laufe zum Supermarkt.' Most Germans (I believe) will understand: I'm walking to the supermarket. Austrians and some Germans will unterstand: I'm running to the supermarket. If you say 'Ich gehe zum Supermarkt', it can either mean 'I'm walking to the supermarket' or 'I'm going to the supermarket' (which includes the possibility that you go there by car). You can use both 'gehen' and 'laufen' for people. When talking about animals I'd use 'laufen'. 'Das Pferd geht über die Weide' is also possibly but sounds weird.