Can you recommend me a good mobile wallet?
Check out Unstoppable.money wallet, it is available for both Android and iOS devices.
This is open source wallet that is working very good for Bitcoin and few other coins, but if you want to have better security than I would connect your mobile wallet with another airgapped device.
For this purpose you can use hardware wallets (Passport, Keystone, Coldcard, etc) or any old smartphone or laptop that are offline.
Another interesting open source wallet is Airgap.it, this can also work with old smartphones as airgapped device.