I know one stands for "slow than expected" and the other for turnover "earlier". In some cases, I cannot explain to myself their position in sentences. Can you explain to me in more detail the meaning of ? And the difference between 才是，就是
I assume you are talking about them being used to describe the sequence of events-- both terms have many many unrelated uses and are very complicated characters. If you clarify these types of questions a bit more it will avoid possible confusion, and it will help make sure you get better answers :)
if in doubt including example sentences for grammar/vocab use questions is always best-- context is king in chinese.
At the basics the two are opposites, early vs late. However chinese isn't ever that firmly set in stone. Here is an article from allset learning chinese wiki, a great source for basic grammar questions if you haven't seen it before:
This should help get an idea of the common use for sequence of events with these terms.
才 has multiple uses. It can be used to indicate "unexpected delay or late in arrival", such as "你怎麼才來呢？" - "How come you come/arrive so late?" When used with 是(is, am, are), it emphasizes one's own argument against the other's argument with certainty, for example:
- 我不是賊, 你才是. - I am not a thief, you certainly/indeed are (a thief).
Same to 才, 就 has many uses. It can be used to indicate something "turned... earlier" without noticing, or simply "already", such as "他早就長大了" - "He has grown up already", which really means "He has turned into a man in earlier days without your noticing."
When used with 是, it can mean "only/merely",
- 大家都来了,就是小林还没有来 - Everybody has came already, only 小林 has not yet arrived.
or mean "even if",
- 就是下雨,我们也要开工 - Even if it is raining, we will start working anyway.
and as a conjunction - "either ... or"
- 这几天,不是刮风,就是下雨 - These few days, either windy or rainy.
Let's compare 才是 and 就是 using previous example:
A: 你是賊. (A simple accusation/argument.)
B: 我不是賊, 你才是. (才 emphasis own accusation/argument in hit back.)
A: 你就是賊. (就 supports the original accusation/argument with emphasis.)