@afreak, Tomáš, For the inexperienced and with out access to equipment, It looks like the way to go may be to change the screen assy.. Find guides below to see how both the screen assy. is changed and a video showing glass only repair. In both cases the phone is dissembled. Last link is te replacement parts which you can do a search on for better pricing perhaps. Good luck. I hope this helped you out, if so let me know by pressing the helpful button.
[guide|92153]
https://www.youtube.com/watch?v=J6xLl8-Z_1M
https://www.aliexpress.com/popular/samsung-galaxy-a3-2016-screen-replacement.html