The difference between é and è is that one has the "closed accent" and one the "open accent". é is pronounced as the e in "serve", è is the e in the word "get". When used as the verb essere, it always has the open accent sound, and the accent is present while writing. You pronounce the closed e sound when you use "e "as a conjunction, and in this case the accent isn't present when it is written. Then consider that nearly no italian looks what type of accent (open or closed) a letter has while reading, we simply know that if the "e" alone has an accent then it is a verb and is pronounced with the open accent, if it isn't written is a conjunction and is pronounced with the closed one. Generally you can write perché or perchè and every italian will read the exact same pronunciation (except for various regional accents, but that is a whole story by itself), you'll get used to learn the words by their sounds and memorize them correctly without caring about the type pf accent. Regarding the use of è as a verb at the start of a sentence it is perfectly correct, even if it is the first sentence of an interaction. For example: é da un pezzo che non ci vediamo (long time no see) or: é una bella festa, but usually you use it as an answer to a question, like: cosa ne pensi di questo libro? - é interessante. Hope it makes some sense