• Ijtihad is the disciplined effort of a properly qualified scholar who uses the required knowledge and principles to determine a Shariah ruling from its evidence.
• Istinbat means drawing or deriving a ruling from its evidence through that disciplined scholarly method.
• Learning an introductory map of Usul al-Fiqh helps you understand how this discipline works, but it does not by itself provide the knowledge, training and qualifications needed for independent Ijtihad or issuing new rulings.
Your goal here is to follow the reasoning accurately: source → wording and context → relevant principle → limited understanding.