I have two questions.

I have an sd card that worked perfectly in a Note 3, class 10 etc. In the S7 it seems to have a lot of problems being read at times and can be very slow.
Is this a phone issue or the card?
(still works perfectly in note 3)

Are there any recommendations for a case for the S7? I am looking at the

Lastly, I know I said two questions, do the screen protectors only protect from fingerprints, scratches etc or do they also reduce the chance of the screen cracking if you drop the phone.