Evidence Act vs BSB vs BSA: Humein kaisa lage?

Yaar, main to evidence mein stuck hua hoon. Evidence Act, BSB (Best Evidence Rule), aur BSA (Best Secondary Evidence) - yaar samajh nahi aa rahi. Sab kuch relate karne ki koshish kar raha hoon, lekin kuch nahi chal raha. Humein kaise decide karna hai ki primary document main evidence kaa sahayog kiya jaa saktaa hai ya phir secondary evidence ka kaam leta hai? Aur phir BSB ka connection kitna hi confused ho raha hai. Main toh khada ho gaya hoon, please help karein. Kisi ne to kuchh clear explanation share kare, main toh akele hi confuse ho raha hoon.