Is there a way to increase the storage?

[jiapei100]

I don't think you can replace the eMMC directly (happy to be corrected if I'm wrong).
You can however, insert a SD card (directly above the SIM card) with as big a storage as you like.
I'm not sure how the different distros handle the SD card (automount, mount when accessing in filemanager),
Mobian f.e. mounts it on access.

Thank you man...
That's great... But, can I have dual boot for the phone? Or, it's just for storage, but cannot boot?