Phoenix Wallet is a safe method for using Bitcoin if you are not using a hardware wallet or a "multisignature" custody setup.
The wallet is open-source and has been reviewed independently to make sure there is no malware or backdoor.
The developers cannot have access to your Bitcoin wallet.
The private keys that control the Bitcoin are encrypted on your phone. To spend money, you must decrypt your device with your biometrics.
Phoenix Wallet protects you well against non-hacker people that gain access to your phone.
Phoenix Wallet is more vulnerable to malware and hackers than hardware wallets.
Phoenix Wallet lets you create backups easily and securely which let you recover access to your money if your phone is damaged, lost or stolen.
See their Codebase
Additional Documentation
Telegram support group