Who am i to believe a bi. t.c. h when i dont believe myself?

Pierre: parle doucement, s’il te plaît! a. his parents b. his teachers c. his friend d. his neighbors

Using the prepositions as a hint, choose the correct conjugation of the appropriate verb. je __ a la bibliotheque avec ma soeur. -vais-va-vas-viens

Explain what has to happen when you use être instead of avoir for the formation of the passé composé? il an english explanation with steps if possible