What the difference between “不” and“没”

没：否定客观事实 比如：他昨天没出去。
不：否定主观意愿 比如：明天他不来。

不：一般进行时、一般现在时、一般将来时等表示现在/将来状态的时候用【不】，如：不去，不要
没：一般过去式、过去完成时、现在完成时等表示过去/完成状态的时候用【没】，如：没去，没要
比如这些词语中，不去表示不想（更侧重于主观）没去表示已经发生了 。

Hi, please check the dictionary for 不 vs 没
https://www.cchatty.com/grammar/10342

To say it simply
不 is used to negate present or future verbs like : 我不吃 means I don't eat or i wont eat
没 is use to negate past verbs like: 我没吃 means i didnt eat
Note: 没=没有 so you can say 我没有吃 also means i didnt eat
For continuous verbs we also use 没 to negate for example: 我在吃饭 becomes 我没（在）吃饭/我没吃饭 which means im not eating

你要问的是“没”和“不”的区别吧？
今年冬天没冷，语法不对，不可以用“没”，因为不是发生在过去的。
正确：今年冬天不冷。

“不”用来描述现在/未来的事情，
“没”用来描述过去的事情。
“你去上海吗？”
“我不去。”
“你去过上海吗？”
“我没去过。”

今年冬天没冷should be something like 今年冬天没冷过 or 今年冬天还没冷。

还mainly has two meanings:1.when it reads "huan", meaning give something back to someone,e.g. 还钱，basically means "better give my money back" 2. when it reads "hai", it is an adverb( not verb anymore), meaning "still ",like"你咋还在这？"(why are you still here?) it's a bit hard to describe, but basically when it's used as an adverb, it has a meaning of consistency(持续) and usually has a negative conotation

今年冬天没冷 (wrong)
今年冬天不冷 (right)

还和没的区别很大，还：当你发音念hai，意思：当你已经有一些东西，你需要要多的时候，你就可以用这个词，例如：我吃了一碗饭，还要一碗。当你发言念huan，意思：将一个东西给回别人，例如：你什么时候还钱给我？把我的手机还给我。没：表达某些东西或者感情不存在了。今年冬天不冷，必须用“不”，因为冷是形容词，不能用“没”，名词前面可以用没。“不”和“还”看上去很像，但意思完全不一样，要注意了。