Keep Coding

i know this might look silly, but i am a student really need help to completely understand how the OTP works , code , classes for a school research
any recommendation from where to start or what to read ?
really will appreciate the help

try to take a look at the documentation of OpenTripPlanner at the following link:
http://docs.opentripplanner.org/en/latest/
For the algorithms used take a look at the 'Bibliography' section.
Long story short,
OTP uses different algorithms for different problems. Most of them are Dijkstra based.