Will I get the money back to my laptop immediately?

My display flickers but it came out of nowhere. When sitting. Can I use it to go to Media Markt and claim the money back after a six-month guarantee?

First try with the warranty

Guarantee is a voluntary service by the manufacturer (not Mediamarkt)

Then you can contact the manufacturer

How old is the laptop?

That depends on the media market. The manufacturer can also repair / improve the product

After half a year, well it will most likely be sent for repair.