I will talk about exact instances in later posts, but this at least shows some background into the what and why of polite language.
This is something that both Dutch and Japanese share, though Japanese is stricter than Dutch.
Since this is more of a cultural things and less about learning lists of words the format will be slightly different.
What is polite language?
Polite language is a form of language that you use against those who are older, those you don't know and any other moment you need to be polite. Things like teachers, bosses, your grandparents, etc.
Why do you need to pay attention to polite language?
Because you don't want to be seen as being rude or nasty. It's like learning to say "thank you" when you get something, but then there are multiple versions depending on who you're thanking.
In Dutch there are only 2 versions, polite and informal, and the rules for each are not that difficult and totally depend on who you're talking to. Though it is always the best to use polite language when you're talking to someone for the first time.
In Japanese... There are more ways of differentiating between polite and impolite language, it influences almost any conversation you'll have.
English: Thank you
Dutch polite: Dank u (wel)
Dutch informal: Dank je (wel)
Japanese polite: ありがとうございます
Japanese informal: ありがとう
Dutch polite: U
Dutch informal: Jij
Japanese polite: あなた
Japanese informal: 君(きみ), お前(おまえ)
Japanese rude: 貴様(きさま), 手前(てめえ), 己(おのれ)
As you can see English only has a single form of you, no matter the formality, Japanese has 6, and there are more that I haven't even listed.
Polite language is a big part of a culture. In Dutch you will use polite language to people in shops, to people who are older than you, etc. In Japanese there are special ways to talk to women, to talk to your boss and to even talk to state officials. Sure, some you'll most likely never use and some you'll use all the time, depending on your age or status.
A good rule of thumb is to always use polite language in situations where you aren't sure.
The reverse sometimes counts for me, I sometimes feel weird to say "you" to someone who is older or a teacher I respect or something. For me, I should call them "u" not "jij", which you implies for me. For me it is such a part of my culture that switching to a less formal language sometimes leaves me feeling like I'm being rude.
So, no matter if you're feeling very formal to people, chances are, it is simply part of their culture. Also, people will usually tell you when they think you're being too formal. It's better to be too formal than not formal enough. Nobody likes rude people.
Does your native language have this difference between polite and impolite? Or does any other language you know have this difference?