If I were you, I.(buy) these shoes​

if i were you, i would buy these shoes

чтобы начинать, чтобы начинаться

все ваши предложения в прошедшем времени,поэтому используем past perfect passive.

they said the medicine had been prescribed by the doctor.

  he understood that the house had been robbed by the thieves.

  she said he had been seen the night before with a pretty girl in the club.

  he said that his walkman had been given to him by his mother as