Genki I Chapter 12

It turns the sentence into an explanation. When you use だ or です you're merely stating a fact or making an observation. Using のです adds a sort of explanatory nuance to the sentence.

If it's noun or な-adjective you add な before のです.

Why

What?

Too much.

You can add すぎる to a verb/adjective/noun stem to say you've done too much (verb) or something is too much (adjective).

食べる ➜ 食べ ➜ 食べすぎる or
高い ➜ 高 ➜ 高すぎる
赤 ➜ 赤すぎる

"Not enough" The negative usage of すぎる.

Past tense of すぎる. For past tense you conjugate すぎる, but for "too little" you conjugate the verb or whatever.

Sometimes すぎる will show up as a noun instead of a verb. The rules and meaning behind it are still the same.

By the way...

"You should (verb)"

"You shouldn't (verb)"

Pretty similar in usage to から, except ので is used after a clause that is undeniably the truth. You cannot use ので with assumptions and such.

Short form verb + ので
い-adjective + ので
な-adjective/noun + な + ので

"Don't worry about it"

"Must" Make a word negative, drop い, add なければいけない. You can replace なければ with なきゃ instead. And in spoken language, you can often shorten the whole thing down to just なきゃ or something similar.

By all means

Boring

"Probably."

Using でしょう to ask a question is a bit more polite. It's like asking someone, "What do you probably know about this?" You're assuming they know the answer, but if they don't that's fine. ですか makes it seem like you know they know the answer and you're putting them on the spot.

"Right?"