Which keyboard are you using? Go to settings/general management/keyboard list and default. For Samsung, tap the Samsung keyboard and turn off predictive text, auto replace and suggest text corrections. For Gboard, select Gboard settings/text correction and do the same. You can also accomplish this by tapping the settings gear on the respective keyboard. If the gear is not visible, you can tap the "more" icon on the keyboard to bring up the additional tools, which will show the settings gear
