Yes! You — and only you — control the private keys in your Slope Wallet.
Your private keys (all derived from your recovery phrase) never leave the Slope Wallet app. The only way to get them out is when you reveal the recovery phrase. So handle it with great care!
No-one, not the Slope Wallet team, not the backend, not any of the DApps or other mobile apps, no-one can access to the private keys from your wallet. Whenever an operation is needed that requires the private key, Slope Wallet only signs a message with the private keys, without revealing it.