Why should not i download from google play store ? Is there any problem with it ? What's different between .APK file and the one available in google playstore ?
There are copycats on the Google Playstore that have not been removed or monitored by Google itself. That's why if you're going to download an APK, make sure that you're getting it from the official website. They have their own link on their website and that's to help you avoid downloading the fake ones. Many have been victimized by those fake wallet apps because they clearly look similar to the official one and that's why if you're going to download through the play store, be careful and do it with diligence.
I open the electurm website and then click on the Play store link and it directly took me to the right wallet. Also i saw high number of downloads. So by doing so, i landed at the right wallet ?
Just to be safe, go to the official website of Electrum which is
https://electrum.org/#download, and download the android version there.
In Google Play, just to avoid the potential scam apps, some of them also have a high number of downloads. See in the official website if the link is the same as what it's indicated, there's the link for google play there.