The only reason I can't use Samsung keyboard is because I write constantly in 2 different languages, and on Samsung keyboard you have to choose the language you want to write beforehand, and of course I constantly forget to change it, until I notice its not correcting my mistakes. So I end up using SwiftKey which identifies the language. If Samsung fixed that it would be a way better app.
In Samsung Keyboard settings, there are 2 options - Auto replace and Suggest text corrections. You can add languages there. Check if these options help.