@hermanmaye I don't even think Garmin does repairs. I'd try a Google search and check for places that specialize in that type of repair. Places [https://satnavrepairservice.com/repair-satnav/garmin-repair/garmin-dezl-770-repair/2098.html|like this] could be an option.
Now, this is not to say that you can't repair it yourself. Let us know what is wrong with it.....maybe you can save some money and fix it yourself.