The cell phone, a Huawei, of a friend of mine has started to burn even though it was only connected to the charging cable. Can that be the case and can you then demand the money back from the respective market?
Of course, this can happen, but it shouldn't. Depending on the age and damage of the device, it will be replaced.
If it caught fire, definitely. If not, make it public on social media. If enough people see it, you will surely get one sent quickly to maintain the good image.
If there's still a guarantee, just exchange it
It was still relatively new as far as I know it still had a guarantee
Could he have a good chance. However, if it has been badly damaged or bent beforehand, the dealer can certainly refuse.
This can happen every now and then if the battery is defective, and if your Huawei has a lithium polymer battery, such as the Huawei P30 and P30 Lite, a defect in the charger or the charging electronics can quickly trigger a battery fire, this is a warranty case and the dealer has to provide replacement
https://www.sueddeutsche.de/digital/lithium-ionen-akkus-warum-smartphones-ploetzlich-feuer-fangen-1.3198405
https://www.elektroniknet.de/power/lithium-polymer-akku-loeste-grossbrand-aus-126631.html
Seems caught, not helpful!