This is a very difficult project for someone with no experience with Arduino. We strongly suggest that you start at the beginning.
Get an Arduino, learn to blink an LED without using delay, read a switch, measure a voltage, a temperature, etc. in order to learn the language and special features of the Arduino. If you skip those steps, expect endless frustration.
When you have done all that, google "arduino temperature control" for lots of examples. Measuring conductivity is a completely separate topic.