message saying "disable harmful apps Galaxy apps can damage your device" I got this message on my Samsung Galaxy trend Plus but not sure what to do. Not very tech savvy anyone got any advice? 

thank you
Galaxy Apps is Samsung's Appstore for its own software, which are usually variants of apps produced and distributed by Google through Google Play Store. There is generally a complement app for every Google App. Galaxy Apps, the Appstore frontend, is not unsafe, but it can be a propaganda spread by other appstores and virus checkers to dissuade you from downloading and using Samsung APKs there. The official opinion is that ANY APKs distributed through any appstore than Google's Play Store can be unsafe, and as a consequence, to install Galaxy Apps distributed APKs demands the permission "Install unknown/outside apps". Something is warning you about this setting; accept the warning under this understanding or remove whatever checking is in place.

EDIT: as of my Samsung Galaxy S8, or possibly earlier, Galaxy Apps CANNOT be disabled, so while whatever is possibly reporting a false safety warning, it may also be hinting that the app may be unsafe but can be corrected with a more current update?