Como decir en Ingles: "disculpe ud, pero me perdi durante su explicacion"
"me perdi" en el sentido de perderse al escuchar una explicacion de alguien o
perderse leyendo un texto

perderse, como sinonimo de "no enteder"se dice

sorry, I missed, could you please explain again?

ó

sorry I'm lost, could you please tell me again?

Question

Como decir en Ingles: "disculpe ud, pero me perdi durante su explicacion"
"me perdi" en el sentido de perderse al escuchar una explicacion de alguien o 
perderse leyendo un texto

perderse, como sinonimo de "no enteder"se dice 

sorry, I missed, could you please explain again? 

ó 

sorry I'm lost, could you please tell me again?

Answer

Sorry, I missed that, could you please say it again?

Answer

Informally you could just say, "You lost me there.", or "Well, you lost me on that.".

A little more polite, but still informal is "Sorry, you lost me".

A little more formal is "Excuse me, but I didn't completely follow you (there, in that, on that one, etc.)".

or you could just say "Would you mind going (running) through that again for me?"