How to format a SanDisk microSD card?

Question

Memory cards

There is a memory card SanDisk Ultra 64gb 10class A1.
The card is half a year old, and was only in the phone and the data from it was no longer displayed on the phone. When you try to write data, they are allegedly recorded but immediately disappear.

Answer 1

No way. She died. Back up the data if there is anything, because soon it will no longer be read /

Answer 2

Return under warranty