You cannot download the official Gmail app on BB10. However, BlackBerry has an excellent native email client.
Because these devices are built on Android, they support the full range of Google services with seamless synchronization across all your devices. Google for BlackBerry 10 (BB10) Devices google for blackberry download
If you own a newer BlackBerry device like the KEYone, KEY2, or Motion, your phone runs on the Android operating system. This means you have native access to the Google Play Store. To get Google apps on these devices: Open the Google Play Store app. Sign in with your Google Account. You cannot download the official Gmail app on BB10
Use Cobalt’s Play Store: Many enthusiasts use a third-party tool created by a developer named Cobalt to sideload the Google Play Store. google for blackberry download