So this is how I repaired it.
I removed the sd card and deleted all the content on it, then placed it back.
I installed the garmin usb drivers.
Downloaded the Garmin cure 3 and an original fw, made a cure version of it. This program runs only if u run it as administrator.
I connected the gps to the pc and turned it off by long pressing the power button.
I started the cure program and after that the updater app. I selected Usb.
I moved the cursor over rhe ok button, vecsuse you have to be very quick, literally 1second what u have
After that i hold pressing the upper left corner of the gps unit + the power button.
The gps will show up for a sec in the updater app and the windows beeps one time, here you have to click on the ok very very fast.
I had to do this holding the screen+power combo once more since it disconnected after that 1 sec.and clicked on the update again very fast.
The gps gome into preboot mode and flashed with the cure fw.
Now the pc sees the internal memory. I deleted everything in the map, voice, gpx folder.
With the cure program and the updater i flashed now the original fw back on it.
Now it can be seen normally in the express, so i registered it and did a fw update in the express again.
I doenloaded in the express the latest map update and waited an hour or 1.5 to download and install the maps.
I restarted the unit and voila, after the initial setup (language, units etc) it works fine.
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