<span>Él es un compañero de clase is the right answer. The 1st sentence is ella but </span>compañero should be compañera. In the second one ella should not have an accent mark and in the last one el doesn't match with una.
Eres paciente pero divertido
"Eres" already implies the person it's talking to (you, in this case), if we wanted to make it formal, we would've used "Usted es" (You (formal) are)
"Pare para cuando hay peatones en el cruce" This means stop for pedestrians in the crosswalk.
