This process will completely shift the app storage burden on internal storage to the SD card, the system will secure and adopt the SD card as its own and hence lift all restrictions as to access from apps.
The instruction below will solve your smartphones low storage issue as it allows the system to install apps on SD card directly (once adopted as internal), even with complete data and obb files. Carefully follow the steps below to get it done.
Note: Original SD card is required, otherwise it won't last long on the device. If you are using the old Micro SD card, make sure you backup all your files and documents.
To Use SD Card As Default Internal Storage on Android 6.0
1. Switch OFF your smartphone >> insert the original SD card you wish to use as internal storage >> Turn it ON again. You should get a notification - "New SD card detected", double-click the notification.
2. Tick Use as internal storage, then click on Next
3. Before you proceed, remember to back up all your files in a safe place (Save your files/documents on your PC or use another SD card).
4. Now, click Erase & Format (wait while the SD card getting formatted).
5. Tick Move now or Move later depending on when you wish to move media files from the internal storage to the newly prepared SD card.
6. Click Done and reboot your device.
You are done, your SD card will now perform the function of internal memory. Any app you download from any source will be automatically installed into your SD card as default memory.
The process will make your SD card secure and ties it to your smartphone only. Once you format your external SD card as an internal storage on Android 6.0 Marshmallow, it can only be used in the same device then. To use it on other devices, a format will be required, which ensures the safety of your data on the SD card.