"I do not know this dog."
Translation:Ja nie znam tego psa.
What's the difference between "znać" and "wiedzieć"? Any analogy from the German or the English language?
kennen – conoscere – to be familar - znać
wissen – sapere – to have knowledge or information about sth - wiedzieć
Im willing to be corrected but "tamtego" would be equivalent to "that" ... "tego" is "this"
"znać" is "to be familiar with", so mostly (if not exclusively) "to know X".
"wiedzieć" is "to have some knowledge", so mostly "to know, that X", "to know about X", and similar.
Is the "ja" really necessary or can you just drop it? If so, what is the difference?
It's totally redundant. The subject of the sentence is obvious from the form of the verb.
Well, that's just wrong. Firstly, you have "Znam tego psa" (I know this dog) in Accusative. It's 'tego' because in Accusative, it actually matters whether a masculine noun is animate or inanimate. A dog obviously is animate. So the noun phrase is identical to Genitive. Therefore you have "Znam tego psa" and "Nie znam tego psa", although they use different cases which just happen to be identical.
If you use an inanimate masculine noun, the Accusative form is identical to Nominative.
"Ten dom jest duży" (This house is big), "Znam ten dom!" (I know this house!) and then, Genitive "Nie znam tego domu" (I do not know this house) isn't like Accusative at all.