"Bye, good night!"
Translation:Ahoj, dobrou noc!
The accusative case (abbreviated acc) of a noun is the grammatical case used to mark the direct object of a transitive verb. The same case is used in many languages for the objects of (some or all) prepositions. It is a noun that is having something done to it, usually used together (such as in Latin) with the nominative case. For example, "they" in English is nominative; "them" is accusative. The sentence "They like them" shows the nominative case and accusative case working in conjunction using the same base word. The syntactic functions of the accusative consist of designating the immediate object of an action, the intended result, the goal of a motion, and the extent of an action.[1
The accusative form is used, because it's short for "I (nominative) wish you a good night (accusative)". Actually, dobrý den/dobré ráno/dobrý večer are also accusatives. It' s just not as obvious as for feminine nouns, as the nominative and accusative forms are identical for neuters and inanimate masculines.
C is the voiceless alveolar affricate https://en.wikipedia.org/wiki/Voiceless_alveolar_affricate The IPA symbol is actually t͡s so it is really a connection of t and s in some sense. Note, that c (děcko) and ts (dětský) are distinct in Czech and sound differently.
See the Tips and notes for the fist skills for tips about Czech orthography and pronunciation. You can also read other resources like https://en.wikipedia.org/wiki/Czech_phonology