If I deactivated my account, Does it mean I will lose all my day streaks and language levels ? I will be back, but I will deactivate it for 16 days for personal reason, but at the same time I don't want to lose my days streaks and language levels
Unless you have a specific reason for actually deactivating your account, it might be easier just to not visit Duolingo for sixteen days. Doing this, you will lose your streak, but you won't lose your language levels.
Yes, as dancepointe said, you won't lose your progress besides your day streaks if you just don't get on Duolingo for 16 days. I didn't use Duolingo for a period of about 4 months (maybe longer), and all that happened was that all of my categories needed strengthened and I lost my streak.