My App download is decreased dramatically in Google Play

Hello,
I have developed many app and game that are in Google Play. When I published my new application “Make Me Old” within in a week it was downloaded 5000 and in second week download increased to 7000. After second week, download decreasing and now this application is downloaded about 2500 only in a week. This incident happens with many of my application. Can any one suggest me how to increase download as it was in second week.

Thanks,

This doesn’t really come under “Advertising Networks”…

It could be related to a number of things:
Trending You might have gotten into the trending section, but then gradually fell down the trending list, decreasing downloads.
Competition Another app doing a similar/same thing might have been released, by chance or after seeing your app, taking downloads from yours.
The first 30 days During the first month Google allows new apps to climb up charts easier and doesn’t apply the same search algorithms to these new apps, giving them a chance to get seen over the saturated market. This effect ceases after 30 days, where your downloads can decrease big time.
Natural Fluctuation Sometimes it’s just random fluctuation due to a number of variables in the mobile world. There are so many factors that can cause this that there’s no point in listing them.
I have experienced all of these across my apps, and a lot of the time there’s not much you can do, but watch the numbers change.
The best thing you can do is to make sure your app is the best of it’s kind across the board.

Or you’ve got some bad reviews that are visible at the top for countries where you were popular.