Do you have a card Reader?
In you case, you could try to connect this SD card to your computer with a card Reader and see whether it could recognized functionally there.
If this SD card could be read well, you'd better back up all your saved data inside it on another drive or storage device and format it to fix its problems. Finally, plunge it to your Android phone and check it again.
But, if this card cannot be read normally and get the same problems, you'd better use a SD card data recovery freeware to restore your saved data back and then replace it with a new one.
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Remember: Always back up everything important on different storage devices or locations.