@Mirko75
You didn't enter the model number, so I'm having to guess that this is a laptop -- but this issue means that the screen is dying and this is only going to get worse and worse until it fails completely. You will need to look into getting the screen replaced.
We are not able, or permitted, to provide any repair estimates or equipment prices.
For this information, you would need to contact an HP Repair or Service Center.
Since you live outside the U.S., here is a link to HP Service Centers, by Country/Region: https://support.hp.com/in-en/service-center
If that link does not provide you sufficient information, then use the main HP link:
https://support.hp.com/us-en/contact-hp?openCLC=true
I've found those links to be unreliable if you're using Win10 and the new Edge Browser; so if you are, you need to use something else, like FireFox.
Good Luck
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