German phrase
Ich schreibe kurz, ~.
Meaning
I'll keep this brief: ___
When to use it
It means you will be brief. Common in polite, matter-of-fact emails or messages.
Example dialogue
Ich schreibe kurz, um zu fragen, ob du heute Zeit hast.
I'm writing briefly to ask whether you have time today.
Ja, ich habe heute am Nachmittag Zeit.
Yes, I have time this afternoon.