Edit-Aku is informal for 'I' they mix formal and informal a lot throughout the course.
Informal for "you" is kamu. "Lu" is more like a slang/urban words.
The formal version of "you" is : "Anda"
Informal version : "Kamu"
Slang version : "Lu" "lo" "qmu" etc
"me-" is a prefix that is used to show that the verb is in active voice, or sometimes this prefix is used to change a noun or an adjective to become a verb.
"Saya" is more polite than "Aku". "Saya" is used when talking to someone with higher status to show respect (teacher, boss) or in a formal situation (meeting, speech).
"Aku" is used casually with someone close to us such as friends, little brother/sister (except to our parents, sometimes it sounds rude)
makan = eat (casual, daily conversation)
memakan = to eat (formal, official document)