Stamina and Receiving serves

Hi Alois and pingskills

I've been improving a lot, my legs are very strong, but today my coach make me a multiball sesion in a high intensity and i get tired too fast, then my level down...how i can imrpove my stamina??
Besides, i improve my backhand flick, but when i can't read the spin of the serve, i don't recieve with decision...for example, my coach has great serves, and i don't know when he put backspin or topspin on the ball, then i go to the ball with ''fear'' that it goes to the net or out of the table...if i read the spin of the ball, i push, hit or flip it, but if i don't read it i'm finished...PLEASE!!GIVE AN ADVICE TO READ ALL THE SERVICES!!!(my weakness is the topspin serve)

HELP and THANKS!!