Although BlueWallet 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 bitcoins are the following:
Someone finds your backup.
This person is often someone in your close surroundings.
You leave your phone open and someone has access to your password.
Your phone stops working or you lose it and you are missing your backup and passphrase.
You brag about your holdings and someone attempts to take them from you through coercive means.
Be careful how you store your seed phrase and passphrase, these are crucial for the recovery of your funds, but are also targets for someone wishing to steal your funds.