What does donc un bref bonne nuit et je suis au lit mean in French?

This phrase doesn't quite make sense in French. Here's why and how to fix it:

* "Donc un bref" doesn't make sense as a phrase. It's likely a combination of "donc" (so) and "un bref" (a brief), but they don't flow together naturally.

* "bonne nuit" is correct, meaning "good night".

* "et je suis au lit" is also correct, meaning "and I'm in bed".

Here are some ways to rephrase the sentence in French:

Option 1 (More natural):

* "Bonne nuit alors, je vais me coucher." (Good night then, I'm going to bed.)

Option 2 (Slightly more informal):

* "Bonne nuit, je suis au lit." (Good night, I'm in bed.)

Option 3 (Adding a bit of personal touch):

* "Bonne nuit, je vais aller dormir." (Good night, I'm going to sleep.)

In summary, while the original phrase might have been intended to convey a meaning, it needs to be revised for it to be grammatically correct and natural sounding in French.