How to Uninstall/Reinstall a custom module whithout losing the content? As we know : it's impossible to unsintall a module whithout being forced to remove all the data that's belongs to it.
The problem is, if we want to update a module we are obliged to uninstall it and then reinstall to get the changes work.

At developpement phase, it's ok , but what about being in a production site and having a big amount of data we don't want to loose, by just adding a field , or changing a type ....

Is there any best practises? Is there a process that could be advised? Is there any feedbacks of your own experience?

For example, I would guess : export data and then import data after the reinstall?

Thank you so much!
You can update your database with 


  hook_update_xx


if your module define hook_shema

https://www.drupal.org/docs/8/api/update-api/updating-database-schema-andor-data-in-drupal-8