iPhone 6 storage full

I purchased an iPhone 6 16gb phone 1 month ago for my wife and the phone is not working properly. Storage full, emails reloading constantly, etc.

MEssages have used up 6gb for some reaSon. I have set auto delete after 30 days. 12 gb used in total.

I have researched and have not found any solutions. Phone keeps freezing up.

THanks