ViaWallet is a decentralized wallet. For assets security, all the user identification contents, including wallet password and mnemonic words will be offline stored on the installation device, thus you'll need to back up and keep them securely. If you forget the wallet password, ViaWallet cannot find it back for you！
The only way to reset the password is to delete the current app, and reset the new password by importing the mnemonic words. You must confirm that the mnemonic words have been backed up correctly before deleting the app.
Find out more details on “How to import the wallet”.