When do you use

不：1.negates the actions in the present or future, 我明天不去学校；我现在不吃饭; 2. negates the habitual actions, 我平常不玩儿游戏；3. negates an adjective, 今天不热；4. for asking questions, 你想不想去北京？

没：1. negates the actions in the past, 我昨天没睡好；2. only ”没“ negates "有“， 没有 do not have; 我没有钱买电脑；3. for making comparision, 咖啡没有茶好喝。

没= don't have, doesn't exsist, didn't
不= no, not

没吃晚饭 = didn't eat dinner
不吃晚饭 = not eating dinner

不 is used for actions that not going to happen
没 is used for actions that have not completed/done
Examples:
我不去学校 I'm not going to school.
我没去学校 I did not go to school./ I have not gone to school.

我不吃晚饭 I don't eat dinner./ I'm not going to eat dinner.
我没吃晚饭 I did not eat dinner./ I have not eaten dinner.

我不说 I won't say it.
我没说 I didn't say it. / I have not said it.

Both “不” and "没" are negative markers, but they are used differently.
"不" can be referred to habitual facts or intentions of not doing something.
e.g.,
我们星期天不上课。
妈妈每天早上不吃面包，只喝咖啡。
我不想去公园，我想去动物园。
"没" indicates things that did not happen in the past.
e.g.,
弟弟昨天没上学。
星期六我们没去打球，因为下大雨。
我没吃过法国菜。

The Chinese words "没" (méi) and "不" (bù) both express negation in Chinese, but they are used in different grammatical contexts and have slightly different connotations.

"没" (méi) is used to indicate that an action or state has not occurred, or that a situation is not as described. It is often used in the present or past tense, and is equivalent to the English "not" or "didn't". For example:

我没吃饭 (wǒ méi chī fàn) = I haven't eaten.
"不" (bù) is a more general negation word, and is used to indicate that something is not the case. It is often used with verbs, adjectives, and nouns to indicate negation. For example:

我不喜欢吃辣的食物 (wǒ bù xǐ huān chī là de shí wù) = I don't like spicy food.
In conclusion, "没" (méi) is used to negate an action or situation, while "不" (bù) is used to negate a general statement or characteristic.

没 is used for the past that you didn't do or didn't have it. 不 is used for speaking about the fact that you don't do something or you are not doing it.