Hi,
I would like to offer you my expertise with microcontroller embedded firmware development, analog and digital hardware design, sensor interfaces, lcd / display interfaces and gui development.
Load cell hardware design, load cell firmware interface and lcd (including alpha numeric, graphical, tft, oled, etc) is something I have experience with and isn't any issue.
Depending on complexity of those calculations I can offer you few solution.
1.) If it is plain simple (basic arithmetic operations) - coding it in C / C++
2.) If there is more to it (fft, corellations, etc) I can offer you to make a algorithm in MATALB and porting it to microcontroller, even using DSP core if there is a need.
However I believe that you need first solution.
10000 PLN is ok, but sadly I don't have opportunity to come to Żyrardów.
Perhaps I can come for few days.
If your project allows you can send me HW which you have and we can work remotely.
Anyway I just wanted to let you know that I'm here, and if this is acceptable for you we can work together.