Samsung S4 soft touch issues

I

I'm not a robot

I've just changed to the S4 from an S5 mini ( hated it) issue is that when I use the softkeys to go back to previous and also when using the internet its either slow to react or in some cases when using internet it will just close out of the page or sure without any keys being touched..getting quite annoying.. is it 5.0.1 or the handset itself ? Sorry for the novel but any help would be appreciated.
 

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