Although Phoenix Wallet is on your phone, the risks of losing funds by getting hacked are very low, unless you are specifically targeted by a highly skilled attacker. The most common causes of people losing their bitcoin are the following:
Someone finds your backup.
This person is often someone in your close surroundings.
You leave your phone open unattended with Phoenix wallet unlocked.
Your phone stops working or you lose it and you are missing your backup.
You brag about your holdings and someone attempts to take them from you through coercive means.
Be careful how you store your seed phrase, this is crucial for the recovery of your funds, but is also a target for someone wishing to steal your funds.