Can I take ferry from Zhuhai Gongbei port to Shenzhen ? How long it takes ? How much ?

No, from Gongbei port, you cannot take ferry. But in Gongbei bus station near the border, there are buses instead, you can take one. The bus ride is about 2 hours, and the fare is CNY100.

If you insist in taking ferry, take local bus no. 99 to Jiuzhou Port in 20-25min. There you can easily take a ferry to SZ in an hour.