Adjusting the font thickness

[Redalexo]

Hello. I use this font on an e-reader (Onyx boox). And in this form, the contrast between bold and regular font is too small. You have to make extra efforts to focus on bold text. I tried all the font options from this post. How can I make the regular part more subtle? To increase the contrast?

[Born2Root]

Hi,
unfortunately it is not that easy adjustable.
It would be necessary to use an base font, that offers different variations like, bold, extra-bold, regular, and light.
Afterwads it would be needed to create a totally new Fast-Font for example with an extra-bold and regular or bold and light typeface.