DW 1a +"formal language" vs. "informal language"

"informal language" and "formal language." I have been talking to my parents in a form of "informal languages" which often ends up an earful of lectures. According to my parents, we as the younger generation has always talked to elders in a "formal languages." They so-called "formal languages" is another form of "standard languages" school has taught us.
I have been arguing with them a lot on the definition of whether they so-called "formal language" is the very definition of academically formal languages.

I remember one time i was sitting in front of dining table when my dad was watching Tv on sofa. "dad, do you that sister Lu has a lot of friends." "how did you know that, did you talk a lot with her on the phone, why don't you folks spend more time on school instead of playing around." Dad scoded. "you two shouldn't date anyone in college, otherwise, you won't have a promising future, you look up your cousin Qing who never date anyone in college." Dad emphasised.
"no, dad, the friends i refer to is merely a friendship not a relationship, what a nonsense are you talking about, sister Lu is not dating anyone, you misunderstood me." I explained. "in that case, you shouldn't say "friends", "friends" refer to either boyfriend or girlfriend, instead, you should say "colleague" she has a lot of colleagues. If you say "friends" then people will refer it to your sister' boyfriend. Doesn't school teach you about the definition of "friends" and "colleague". how come you still make such silly mistake." Dad scoded. "excuse me, that was your "old definition" now friends in present meaning is colleagues, excuse me, your old man." I talked back.
ever since this incident, i have been caustion about the vocabulary i used with my dad, because we are obviously have a big gap.

In my culture, Respect to elders is a must but somehow it doesn't appeal to me. I mean i respect the concept of taking good care of elders in family and respect them when they are talking, however, the elders do not did so to the youngers' generation ( it is my own perspective, my parents thought they did as well as everyone in the family but i don't think so)

"Ivy, you must major in pre-law or medicine, being in college you shouldn't work that much during school time." Mom commanded. "no mom, i don't like medicine, i took anatomy at school and it was difficult without passion." I said. "nonsense, you must slack off, I told you to study medicine, it is good for your future, how come you reject my idean and you are even skeptical about my ideas, how rude you are, i am your mom and i know you better than anyone." Mom shouted. " mom, please show some respects, i din't say that you weren't wrong and i really appreciate your suggestion but i said no, i don't like it, please respect me and i am not child anymore." I said. "how dare you are, ok, fine, you said you are an adult ha, in other word, you mean you don't have to listen to me right, ok, i have raised you up and now you ditched me and you even think that i am annoying. doesn't school teach you that way, showing no respect to elders and being so cocky about yourself, don't you know to be humble, be humble. you, being in school for years are in vain, zip up." Mom scoded.

see, there are obvious gap between us, what is "formal language" and "informal languages." i think the perspective is depend upon people and I hate to say but have to admit there are no uniform defintion of "standard language" which means it needs more time to study.
the most significant one is the first time i stepped in the territory of United States and i have prepared myself for all the "formal languages" i will be encountered in U.S.A. To my surprise, I ain't understand any of them. I was first landing in El Paso, Tx. School placed me in a ESL classes, instead of having students from Asian countries, they are all from Mexico and to a girl like me who couldn'tdistinguish physical differences between Americans and Mexicans, I ended up thinking what my presumptive formal languages that shcool has taught me in China is a completely version here. I don't understand a single word of it. ".dljoejoadjojeojfodjf" a distant conversation. "dljfoeiojelkdjfpw" I was shocked. then, i met these African American people on the bus. " hey, u what up, i ain't done nothing, Fuck, hey u dude, hao thi going," "shit, ...." What was that, i was so lost.
as i walked into classroom, my new teacher greet me with a warmly smile " hello, i am Miss Rose, welcome to our class, what is your name?" she asked. "My name is Ivy, nice to meet you." I responded. "You speaks very good english, did you learn it in China?" she inquired.
"did i really speak a good english, if so, why i didn't understand any of them except Miss Rose?" I pondered.
I have been trying to adopt all forms of language use in United States in order to communicate to various ethnic people. Meanwhile, i ditched my "standard english" i have learned in the past and adopt/perceive oral english as "formal language"
my cousin love AAVE and have been listening hiphop music a lot. whenever he talks i can distinguish his AAE accent.