If you can't install the game, please refer to the guide below and activate 'Install unknown apps’!
1) Android Settings > Biometrics and Security
2) Tap on ‘Install unknown apps‘
3) Enable MY Files or Browser app that was used to download BIRDIE SHOT and then click the downloaded apk again to install. (ex. Chorme)
※ The settings menu may look different depending on your device and operating system