Samsung j3 emerge 2017

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Newbie

Samsung j3 emerge 2017

I got my new phone a month ago and there is no cracks,dents,water damage, etc perfect condition but my back button stopped working and it comes on randomly and turns back off. And when I plug in my Apple headphones my phone starts randomly clicking and exiting out of all my apps. Need answers on how to fix plz and if anyone else encountered this problem thanks.