If the Simpler Trading Mobile App, or any app, crashes on your Galaxy Phone, please try the following steps as a potential fix.
Go to Settings
Apps/App Manager, Select the App that you are having issues with
Tap on "Clear Data" and "Clear Cache"
Restart your smartphone and test
Mobile App - App Crashing on my iPhone / iPad
Mobile App - Troubleshooting
Mobile App - Supported devices and versions (compatibility)