You cannot do that without root. It is useless since in most cases that would only slow your phone down, not to mention that memory cards get corrupted easily.
Thanks for being with Samsung and sharing your concern. We would like to inform you that you the external SD card cannot work as internal memory in the device, however you can optimise the memory by following the below mentioned steps: 1) Optimize Storage Space by scheduled cleaning of phone by navigating into Apps -> Smart Manager/device maintenance -> Storage -> Schedule optimization/S Clean 2) Optimize Storage Space by zipping unused apps by navigating into Apps -> Smart Manager/device maintenance -> Storage -> Zip apps 3) Optimize Storage Space by moving content to memory card by navigating into Apps -> Smart Manager/device maintenance -> Storage -> Move to Memory Card (If option available) 4) Optimize Storage Space by deleting Duplicate images. by navigating into Apps -> Gallery-> Settings ->Delete Duplicate images Be sure to hit ♡ when you find an answer that works for you. For Further assistance, you can get in touch with us via Live Chat option by following- http://livechat.support.samsung.com/Customer_new/IN. You can also connect us via Samsung Members web community by following mentioned url-https://community.samsungmembers.com/en_IN#/
