Hi there! When I download the map of Greece, there are only latin characters but I want the greek ones. What am I doing wrong? Thank you in advance 
If this is a Garmin question, there is a specific Garmin forum on this board, but, in any case you need to tell us which tool you used for the download, and from which server you did the download.
If this is pure OSM, the standard layer will use the name tags, by default, which should be in Greek, for Greece, but other layers favour particular language communities, and will use the language for that community, if present, or a combination of the name tag and that language variant.
Thank you very much for the reply. I downloaded the map from here: http://garmin.openstreetmap.nl to be used in a Garmin Oregon. I am new here, so excuse me for any mistakes
If you follow the forum link on that page, itself, you will end up on the Garmin forum on this board, which is likely to reach people who would know faster.
However, it looks to me as though that site has ready prepared maps, in which case they will probably have been rendered in a language that would be used by someone from Western Europe. My guess is that you will need to use the underlying tools on your own machine. See http://wiki.openstreetmap.org/wiki/OSM_Map_On_Garmin#Creating_your_own_maps_from_OSM_data
Alternatively, search Greek language sites to see if someone in Greece has ready made maps with Greek names.
It looks like Garmin can only handle 8 bit character sets, and you need to have one containing Greek on the device. That might mean that some other characters are unavailable. It looks like that is code page 1253.
hadw, I ll’ try to follow your suggestions, thanks again.