The screen does not contain any data, so replacing the screen does not affect the data on the phone.
However, unless you are doing routine backups, it is just a matter of time before you lose all your data. Once the phone is lost, dropped in the water, or run over by a car, the data will be lost.
Therefore, we recommend to set up a google account on your Samsung Galaxy Smartphone or Tablet to ensure all the data is safe and backed up.