It can happen to you on your Samsung Galaxy S5 that the screen freezes after updating to Android Lollipop and that you can not make any inputs via the touch screen. If that's the case, then there is usually an error in the Software or an System-App, which you can then fix for example with a wipe cache or a factory reset. But first, you must restart the Samsung Galaxy S5, so that one can make again make inputs on the smartphone in Android lollipop.
There is a small key combination that allows to restart the Samsung Galaxy S5 regardless if there are any programs running. This key simulates taking out the battery and is therefore called Soft-Reset, because you do not have to remove the battery ;-)
This feature is ideal when nothing works on your Samsung Galaxy S5 in Android lollipop.
To restart the Samsung Galaxy S5, if no more inputs are possible, simply hold the Power On / Off button for 8 seconds to force the fast shutdown.
Your Samsung Galaxy S5 is restarted after that and Android Lollipop is loaded as usual. Thereafter, you should eliminate the error source. For example by performing a wipe cache partition or to reset the Smartphone with a factory reset.