Is apkmirror.com safe?
Apkmirror.com is run by the same people behind AndroidPolice.com, one of the biggest Android news websites. All uploads are manually vetted and approved, and only free apps are allowed so you won't find any 'cracked' apks or 'warez'.

As you already have the Play Store installed, only an apk signed with the same key as the currently installed version will be able to upgrade the app so this is an extra verification of the apk you download. Therefore, if you download the app from Apkmirror.com you should be safe.

Personally, this one of the only sites I would trust to download apks from.