My phone is mount SD card as \sdcard0 how 2 fix this?

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i just buy a new 32gb mini sd card to make morespace formy vdo files and put to my phone . when i turn it on. The system just mouth new sd card to /sdcard0 then it begin to use as system internal storage. event i try to change default write disk to internal storage that now it show as /Sdcard1. makeme cannot use sd card in full space. please help me.

system: android5.0 , kernal ver. 3.10.54