To free up internal storage on your phone:
Open the Files app and tap 
Or, go to Settings > Storage > Internal shared storage > Free up space.
If there are media files to move, tap the option to free up space.

To move apps to your SD card:
When you install an SD card as internal storage, it is part of your phone. If you want to change the SD card to portable storage or remove it from the phone to reformat and use in another device, first move the apps from SD card storage to your phone's internal storage:
To eject the card, drag the SD card notification down, and tap Eject.
If you don't see the notification:
Next to your SD card name, tap 
It's now safe to remove the card from the phone.
To insert the card into another device (computer, projector, etc.) that uses different card dimensions, you may need the adapter that came with your card. See device manufacturer's instructions for the type of adapter required and insertion instructions.

You'll need to choose one of two formats for your SD card:
| Portable storage | Internal storage | |
|---|---|---|
| Store media (photos, videos, music) | yes | yes |
| Store apps | no | yes |
| Content encrypted | no | yes |
| Read card in other devices | yes | no |
To format the inserted card:

Touch Format as internal or Format.
If you don't see Format as internal, then your phone only supports SD cards formatted as portable storage.
If you formatted as portable storage, be sure to update settings in media apps (like camera, music, and podcast apps), so they use the card to store content you create or download.
If you’re having issues, try these troubleshooting steps.