The serif is placed on the position, where it is logical to fill empty spaces

It's wonderful to see such non-chirographic thinking! Keep it up, and don't let old-fashioned people discourage you.

However, in terms of "filling space":
- It's only part of what serifs do (and to me not a central part).
- Is that really what/all you're doing? Looking at the "w", there must be more.

BTW, you might like to analyze (but not imitate) Rotis Semi-Serif, since Aicher was also interested in leveraging serifs functionally, and not according to their circumstantial origins.

hhp

Thanks. I am actually planing to finish it, because it looks nearly refined to me.
But I posted it to this forum, if there are some fatal/minor adjustments to be made...

It actually started as project how to make rotis semi serif "better", or inspired by.

Yes, the function of the serif is not filling the space. I just change their function for my purposes, and I am trying to keep serifs on baseline to have more "consistent baseline" than in some other semi-serif fonts (rotis and themix).

I was mostly curious how people will read the small texts in the pdf attachment. Some people I showed them samples, at first they were very surprised and claim it very disturbing. After some time, they adapted and they don't see them. Usually new type of type need a time to "became" readable to our eyes. But some of them still have a problem after time :)

Getting useful feedback is a classic paradox, especially for a text face. The people who can potentially give you some great advice -type designers- are tainted by having their own ideas of how it should be done*; this is pretty much a death trap for something that tries to innovate. And the people who can give you the best advice -actual readers- cannot do so explicitly; you're not supposed to point out anything at all to them - certainly not that the font is trying to innovate...

* And creative people are not good at putting themselves in other people's shoes.

So you have to listen to everybody with an open mind, but see clearly what's in your own mind, and follow that. And this is what makes me hesitate to give you more advice, at least in terms of where to [not] put serifs. One thing I will opine though is that the weight difference between the Regular and Bold is too great*. I think your Regular is only slightly light, so I might recommend keeping that as is and making a Bold that's less dark.

* Coming back to Aicher, I guess you don't agree with his philosophy for a Bold. I myself actually do.

BTW, you might want to look at Swagg, although it's not hugely relevant.
http://typographica.org/typeface-reviews/swagg/

hhp

Yes. Probably I am myself conservative as well. :) But posting it here helped me to think about it...

Anyway, thanks for the feedback.

(I think I already saw Swagg before.)

*I dont have knowledge about Aicher's Bold, so I will look at it.

And you are right about the weights. But actually, here I displayed Regular and Black weights (medium and bold will go in between them).

Hello Jan,
I like it. The shape of that serif may look a bit strange, but that is probably a good thing:-)
I tried some form of one-sided serifs myself some time ago: https://www.fontfont.com/fonts/bradlo-slab/bold
Andrej

Oh yes!
I was studying Bradlo during my research as well.
I tried to made my semi-serif more close to the sans category, though.

And, yes, i think it's a good thing, too. :)