Trustwallet is a non-custodial wallet and you should be able to import your seed phrase (mnemonic) into another wallet and access your fund.
Of course, this doesn't mean trustwallet is secure. Trustwallet is close source and we don't know whether they have access to users keys or not. It's also possible that you can't recover some of your altcoins due to not knowing the derivation path used by trustwallet.

The best is to avoid any close source wallet like trustwallet.