sudden surge in download of my apps

My app used to get 50-60 downloads per day. Now suddenly for 5-6 days i am getting 400-500 downlads per day.I have no fkcing idea wtf is going on. I didnt do anything. No marketing or promoting anywhere.
So why there is sudden surge in app downloads is this normal??

ur keyword start ranking in top 250 in different countries, or maybe rank in top free or top new free in categories. is normal and congratz hope it spikes higher for you

Once apon a time my game gets 18K downloads per day from 50 per day within the week.
It happens - google engine discovered your app with specific search requests , i think.

I wana put more games on my app. To redirect ppl to my other games which are collecting dust. But i got feeling that if i update my game my downloads will be back to shit.
Wat you guys think is it good idea to update game. Game is on IOS and not on android.