Arduino nano as ADC and DAC

Hello.

I am currently trying out an raspberry pi 3 for a university project, but it does not have any analog pins. so i would like to know if you could use a Arduino nano to read a analog signal and send it in serial to the Raspberry pi, and how to do it. Also how to take a digital output from the Rasberry and turn it into a PWM signal for a motor to run

You can use one or more Nano or Pro Mini for analog input, and transfer the values to the RasPi by e.g. SPI or I2C. The same for the PWM output, which can be done in parallel to analog reading. A Pro Mini can work at 3.3V, so that it can be powered from the RasPi. The Micro only works at 5V, and requires level shifters for the signal connections to the RasPi, unless you use its USB port for serial data transmission.

The RPi can connect to an I2C bus, so you can also take an ADC like the ADS1115 and read it over I2C. Better resolution for less work and cost than adding an Arduino in the mix. Same for PWM output. There are lots of dedicated PWM chips out there that connect over I2C.