All Jews had to wear yellow stars. The yellow star symbolized that they were Jewish. Elie's dad thought it wasn't a bad thing to wear the yellow star, but that's what lead them to his death.
#2
Everytime Elie says “that night” he's referring to another night in horror, another night he had to face some sort of a curel act by the Nazi’s. Elie feels like his entire life is now a nightmare. Elie is saying he will not forget anything that is happening.
#3
The French girl that Elie meet while he was working said this to Elie to gave him hope and told him not to give up. She told him that what was happening to them would come to an end one day and they would be set free. She told him to keep his anger for another day, when they would be set