One way to overcome that is by taking backup of the application by using Apk Extractor. But what if, you are not able to download the apk to your device in the first place. Also Read Top 5 Ways To Extract .apk from Android (NO ROOT) You want to install an app from play store, but it’s incompatible with your device or not available in your country. Now, what other options do we have? I had the same problem while downloading WhatsApp on my Nexus 7 tablet. One way of doing it will be by Goggling “Apk for ‘app’” but then there is a risk of getting an infected file. So what’s the solution? Well, the good news is, there is an online tool — apps.evozi.com. All you need to do is copy paste the App’s Google play and hit the blue button which says Generate download link. And within seconds, you will get the link to download the apk file. Simple. And it works on both computer and Smartphone.  [Video Tutorial]

Since this service fetches the apk directly from Google play, there is no chance of getting an infected file. And Off course, it can only fetch free Android apps. Video Tutorial: Extract apk From Google Play 

Apps.evozi is a reliable way to extract apk file from Google play. I’ve been using it for 2 years and never had any problem other than some occasional hiccups. Now, There are other applications/extensions that claim to extract apk file from Google play but in return ask for your Google credentials and device ID. Think twice before you use them.