On February 18 I have a flight at 0.20 am at Hong Kong. At which time is the ferry from Zhuhai?

Well, according to your arrival time, there is no ferry between these two places. Thus you are advised to stay at the hotel nearby the Jiuzhou Port and take the direct ferry in the next early morning. The single trip takes around 70 mins.
To Macao-HK Ferry Terminal: 09:00, 11:00, 13:00, 15:00, 18:00, 19:00, 20:00, 21:30
To China Ferry Terminal: 08:00, 10:00, 11:45, 14:00, 16:00, 17:00, 17:30