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My screen has suddenly started to be slow, I click on a icon like bluetooth, it flashes, but never comes on, even if I do it on the settings page. If I press others like phone it takes 5seconds or more to respond.
As a first step please try turning the phone Off and On and check you have no software updates.
Do you have a screen protector fitted ?
This is a common problem for the S7. If you do a Google seach, you will find a lot of information and solutions available. The unresponsible touchscreen issues seem to follow the Nougat update.
You may find a simple back up and reset will solve the issues. However, if after following the advise available from the internet does not solve the problems, it may be worth taking the phone to a Samsung Repair Centre or a Vodafone Store for advise.