PIN locked Z2..... help!

I bought a Xperia Z2 from a unknown person, he showed that the phone was working. After i came home i wanted to use it, but it was pin locked, which i didn't know.... i can't find that person anymore. so i can't get into the phone.

i tried to get in the recovery menu to do a factory reset, but none of the key combinations is working...

is there any way to bypass the password or to reset it?

its on lollipop btw