"Thank you, good night."

Translation: Děkuji, dobrou noc.

[FutureOfDenmark]

why is dobrou?

[endless_sleeper]

You can think of it as a shortening of this phrase: Přeji ti dobrou noc. (I wish you a good night.) The verb needs to be followed by accusative case as was correctly mentioned by BoneheadBass. Dobrou is the accusative form of dobrá.

[BoneheadBass]

"Noc" is feminine and in this sentence it's in the accusative case. So the adjective "dobrá" becomes "dobrou." Hope this helps!

[debonec]

Dekuji

[ChudyBohac]

Think of the accusative case as the "direct object" case.

[VladaFu]

Note that grammatical cases have not been taught at this stage of the course yet.

[McConnell18]

I chose "Děkuji Dobrou" and it was accepted.