I got it working
(happy )
What i did was downloading an new map ´Garmin City Navigator Europe NT 2016.10 ´ which is unlocked i now know 4 sure.
This image i renamed to ´gmapsupp.img ´.
I made a new map on my pc called ´Garmin´ , in this map i placed the ´gmapsupp.img´ .
I formatted the SD card from the garmin nuvi250 on my pc.
Now i copied the map´ garmin ´ with the gmapsupp.img on my pc to the SD card.
I putted back the SD card in my Garmin Nuvi250 and it readed the new map with no problems
Voices, streetnames, everything is working fine now.
Interesting fact is that the cardreader on my pc was defect so i just putted the card in my samsung phone and formatted the card via the menu in the phone it self.
After that i connected the phone with the card in it with an usb cable to my pc and i had to remove only 1 file on the card so that is was empty.
Then i copied the garmin map with the gmapsupp in it from my pc to the SD card in the phone.
After that i took out the SD card of the phone and putted it in the garmin nuvi250.
Its a different way but it worked for me , normally it took 2 hours to copy an image from pc to the garmin and with the above method only 10 minutes.
Thnx for the advices!
I hope i can download the NT 2017 map in the next days and use that version.
For now above method i described worked perfect for this device
edit:
Just got the 2017.10 downloaded + copied on SD card and it works perfect.