Things to note till now
@johnfoss: Thanks for the tips 
I went out to practice a bit, and it feels like I’m on the right track. I’m “better” at the freemount, feeling much more stable than before. Also improved the sucess rate of being able to move forward a bit, so I’m happy 
So I’m just going to write down the things I did up till now, maybe itt will be useful to others.
In the first and the second day I practiced indoors, holding firmly into a pole, just sitting on the uni, getting comfortable first (trying to put all the weight in to the saddle). First only did this with my dominant foot on the lower pedal. Then on the second day I went out to the garden, and tried riding along the fence, which I could do nothing at all :D, the uni always slipped out below me.
Then I practiced just sitting with my non-dominant foot in the lower pedal, which was hard at first, but helped a lot in feeling the balance. Also did a few idles with both feet (grabbing onto the pole of course).
After this, riding along the fence became so much easier. However I noticed that because of the comfort of the fence I didn’t really try to let go, so I decieded to try to learn mounting, and with that practice the riding without the fence.
Well, it is a tough one. First I tried with grabbing onto a pole, and push the closer pedal down with my dominant foot, bringing the uni below me. This wasn’t so hard, but without a pole I could do nothing. Even if I could stay on the uni for a little time, I could not start riding with the 6-12 pedal positions.
So this didn’t really helped mounting, but I think it was useful to get used to the uni, feel the balance, and to learn what happens if I put my weight on one pedal.
I did this for days, and at some moment, I just realized, what should I do, how to make it work. The key factor was, for one thing, to position the closest pedal a bit higher than horizontal, almost even with the forkleg (with the saddle between my legs), and the other is trying NOT to put weight on the pedal, just push the uni a bit forward while jumping, and like this place my other foot to the other pedal. With this my weight is much more on the saddle, and I also start out with a 9-3 pedal position from I can start riding.
I’m kinda doing it like in this video:
First it was really hard to try to maintain the balance after the mount, but I found out, that if I look ahead, and concentrate my vision in one fixed point (index lamp of the car in the garage in my case) really helps a lot.
And this is where I stand now, half of the times I can stay a bit on the uni, quarter of the times do at least a half rev, few times a little bit more.
@MissScooties: I feel like learning to mount like this helps me more, than doing rides along the fence, but that’s just me 
I read everywhere to learn to ride first, because freemount is kinda useless if you can’t ride from it, but well, I think I’m trying to learn both at once.
Try it out, maybe it helps you too.
What I think really important at first is to really be comfortable in the seat, and also don’t be afraid of falling (because you can’t really fall that big).
And also they say it’s not really about skill or balance, it’s much more about patience and persistance, so just don’t give up 