Razer Phone 2 SD card

So I purchased a SD card [ Lexar High-Performance 633x 512GB microSDXC UHS-I Card with SD Adapter (LSDMI512BBNL633A)] and installed it as part of the internal memory, as I had consumed most of the available memory on the phone. The problem seems to be that the devise has slowed down, A LOT!! It's almost unusable....Can I make the SD card a portable devise instead of internal memory? How? Also, What does it do to the data stored in it? Will it be lost? Thanks for all your help with this.