Hello !
Can someone explain to me how to change map in my Nuvi 5000 atl,please?

In the 5000 maps can be stored either in the internal Garmin folder or in a Garmin folder of an SD card. On-board you can use several names for detail maps, gmapprom.img for the primary map and gmapsupp.img for a supplementary map. You can probably also use gmapprom1.img or gmapsup2.img and maybe gmapoem.img as well but the latter won't be deselectable in the map info page of settings. On the card only gmapsupp.img can be used in the Garmin root folder. If using 'unofficial' maps you'd be wise not to put them in the internal memory only on SD card. Why? Because if you brick a 5000 or any other Linux OS Garmin device because of a corrupt file internally there is little chance of restoring it because cure firmware is not easily made. It's very easy with Garmin-proprietary OS devices however. If you have a dud file on an SD card simply removing the card removes the problem so no bricked device.