So, after searching for solutions to this problem, i found few things...
First: if you fail fingerprint lock 5 times with turned off (locked) screen, it will show you little grey popup on black background that you failed 5 times etc.. then press lock button, DISPLAY WORKS FINE and you can unlock phone with backup password....
Second: you can download OLedSaver app. it dont solve problem, but makes it lot better
Third:Some users had this solved by instaling Google Play Books and when you read book, there is ¨Aa¨ symbol on top right. In this menu you can turn off night mode and it somehow unbug their phone. Dont work for me....
So its quite clear, its not by hardware malfunction, no expensive repairs needed. Its software bug
Next thing i noticed was that this problem is here for long time and it was even on newer models, but on them it was fixed by update... Samsung aparently dont care about older phones and their users.... they want you to buy new expensive phone.....
Maybe its intentional... idk..
I posting this here, because i found a lot websites and post where they claim that its burned up display and needs replace.... That dont needs to be true, test it! Most of note 9 users have their phone long after warranty and replacing display is expensive and most of all, not necessary. Replacing display will not solve software bug. And with Oledsaver app its quite good, so if you thinking about new phone, try app first. I had to download it from their website, because google play said that this app is not for my version of software.. Not true.. It works fine.
Must say that after this middlefinger from Samsung, i will never buy another product from them. This serves me as example of samsung service...
I hope this help somebody save some money and nerves.
