Greetings, I'm an experienced embedded device programmer(PIC microcontrollers ),Arduino programmer, hardware designer, PCB designer (Eagle CAD).
I understood your project at all, it uses 3 Differential pressure Sensors, a logic level converter to tie 5V Arduino nano logic level with 3V3 logic level of the sensors. Also the I2C multiplexer to expand the I2C port of the Arduino Nano. Iḿ capable to design the PCB according to the rules of the best PCB manufacturers.
Thanks