Share your experience!
I just want to ask if i need to buy screen protector for my screen or not. Is the screen scratching easy ?
Any glass will scratch eventually. To have extra protection, you can buy a screen protector for both back and front.
I'm assuming you have a Z5 and not a Z5c and not in white ?
There are known touchscreen issues with this model and a short term solution mentioned on this forum is to take off the screen protection, which is meant to help with the sensativity.
I have a front and rear tempered glass and also a plastic clear hard cover, so it is well protected, downside is the issues mentioned above 
I have found in the past (on various phones), the tempered glass works better than the little plastic sheets, which tend to have bubbles, you would be hard pushed to get a air bubble using tempered glass ones.
I have kept mine on and will put up with the touchscreen issues until Sony fix it (hopefull).