(بازتاب): reaction and is the farsi word for عکس العمل: accidental reaction
(د) is used for showing surprise in a sentence, like (وا) or wow. In this sentence it means: wow, it is clear (I'm surprised that you didn't know)
(سر در آوردن): to discover, to find out
(کله را به کار انداختن): to think
(حسابی) means very much
I had to think very much
(کش و قوس): when someone straighten his arms, legs or body to full length
(به طرف خورشید میدواند): makes him run towards the sun