Fuse first. But I suspect you knocked a sensor out.

 

left the trunk gate open for about 300 meters

Just a data point - I've left the hatch up many times for a few miles each time when I had lumber loaded on multiple occasions. It never bothered the hatch other than it causing an annoying 'gate open' beep but that quiesced after a bit.

The act of you leaving it up for a few hundred meters was an okay thing to do. Given that, I'm not sure what's wrong with it. I assume you closed it manually and then tried the auto lift function after that a few times - right?

 

Yes tried it many times, disconnected battery overnight and checked too. When I press the "auto lift" button on key (or inside car) it just releases the latch and car liftgate becomes open, but the door doesn't lift up.

 

Open your owner's manual and find the section about fuses. Find out which fuse is responsible for the power liftgate and check it. Replace if burnt. In fact, I would try to replace it with a known working fuse regardless.

 

If the buttons unlatch the hatch, I would think it’s probably not the fuse. When the door is up, does the button on the lid close the hatch?