In Chinese, “if . . . then . . .” is expresse - Cchatty

In Chinese, “if . . . then . . .” is expressed in three levels of formality

Most formal: rúguǒ . . . jiù . . . 如果 . . . 就 . . .
Less formal: yàoshi . . . jiù . . . 要是 . . . 就 . . .
Least formal: . . . de huà, jiù . . . . . . 的话，就 . . .

The IF clause ALWAYS comes first, and the second clause needs a jiù 就. Moreover, the subject in the second clause must come BEFORE jiù 就:

English: If you go, then I’ll go.
Chinese: If you go, I’ll (then) go.
Rúguǒ nǐ qù, wǒ jiù qù.
如果你去，我就去。

OR:

Yàoshi nǐ qù, wǒ jiù qù.
要是你去，我就去。

OR: Nǐ qù de huà, wǒ jiù qù.
你去的话，我就去。

For emphasis, you can combine rúguǒ . . . jiù . . . 如果 . . . 就 . . . with . . . de huà 的话:

If you (should) go, then I’ll go.
Rúguǒ nǐ qù de huà, wǒ jiù qù.
如果你去的话，我就去。

OR:

Yàoshi nǐ qù de huà, wǒ jiù qù.
要是你去的话，我就去。

BUT, when the subject is the same in both clauses, there is no need to repeat the subject:

If you’re sick, (then) don’t go.
Yàoshi (rúguǒ) nǐ bìngle, jiù búyòng qù.
要是 (如果) 你病了，就不用去。