From the main GPS menu, right to the volume icon, choose 'Tools' or whatever you have based on your language (it's a toolbox icon)
then choose the folder icon (my data?) (you my need to scroll down)
next choose eliminate favorite(s) - select All - untick the ones you want to preserve, and that's it!
Alternativelly you can do a soft reset to your device (not a bad idea from time to time) and lose all your personalization data , the maps remain in the device!
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