Hello everyone,
I’m a beginner in type design, and here’s my first study typeface. Could you please point out mistakes that I’ve made here?
It’s done by interpolation between Thin and Heavy, so Black is extrapolated (not that good I suppose). It has no kerning (optical in AI) and no hinting yet. Forgive me for this silly diacritics use, just an example

There’s the whole alphabet in the PDF.
Comments
Anybody else? Please, guys, I need your professional advices
* BTW the "5" nicely follows the "G".
The vertical proportions are problematic. The caps are too large compared to the ascenders* which in turn should be longer than the descenders. I would simply raise the ascenders.
* Unless this design is intended for use in reference works, where proper names should stand out.
Other than that it looks like a good start to me. You should consider designing a Regular though and not leave it up to interpolation (but use the middle weight as a starting point by all means). That will become the most used weight so you need to put time into perfecting the Regular optically.
Check out Stevie Sans for some inspiration: https://typekit.com/fonts/stevie-sans
I agree with Chris that the tail of /g is too weak.
The accents are a bit too close to the letters for my taste, but maybe that's intentional. The /eogonek doesn't work that way, though.