About your Garmin device.
Your Garmin Nuvi 765 are one of the old ones.
You have to use NT maps and NOT NTU maps: City Navigator Europe NT 2016.10
Remember to use/download "FULL unlocked IMG created with MapInstall"
And Second... DON'T delete your Garmin... connect it to Garmin Express and update the firmware, then disconnect again.
Third... You have a' SD-card slot onto your Garmin, buy a' 4 GB SD-Card
Fourth... In your new SD-card.. create a' folder Named: Garmin (remember to use "G" big big letter)
Fifth... Copy your downloaded: *gmapsupp.img* file into your SD-card... Sd-card/Garmin/
Sixth... Go into maps setting into your device... and unpick your old map.... and now pick your newly installed maps.