Re: How do I transfer contacts,photos, messages from my Galaxy S4 to my Galaxy S6
It seems that you still have you're S4 with you so for your contacts you can just have them backed up either to the Google account or the Samsung account then set your S6 so it just backs up all your new contacts to either account that way you don't have to worry about losing your contacts if you have any issues with the phone.
After getting that out of the way you can actually download the Samsung Smart Switch app from the play store and then follow the steps it tells you is very easy and simple app to use. I used it to transfer some old contacts that I had on my iPhone even though I didn't have the phone anymore. All you need to know is the username and password of the accounts on each phone.