Here is how you can create custom login screen
And here is how you can create new account for the user
It’s all in learning pats
If we want to save the data, in the registration form at saving button choose to save action in on-click action like below image and you will be do this using microflow also.
and for retrieve, the data from the database in the microflow add retrieve activity and choose the entity and after that add one more activity for show the page.