Zhǐyǒu xiān liánxì kèfú, wǒmen cái zhīdào zěnme tuìhuò.

This is a very common pattern meaning only if / only when ... then ....

• 只有 introduces the necessary condition.
• 才 introduces the result that happens only after that condition is met.

So:

• 只有先联系客服，我们才知道怎么退货。
• Only if we contact customer service first can we know how to return the goods.

A key point: 只有 is stronger than a plain if. It means this is the only way for the result to happen.

先 means first / beforehand.

In Chinese, adverbs like 先 usually go before the verb they modify, so:

• 先联系 = contact first

Here it shows the order of actions:

1. contact customer service first
2. then know how to return the goods

So 先 is not random—it tells you that this action must happen before anything else.

联系 can be used as a transitive verb, so 联系客服 is perfectly natural and common. It simply means to contact customer service.

You can also say:

• 跟客服联系
• 和客服联系

These versions sound a little more explicit, like get in touch with customer service.

But 联系客服 is very standard, especially in practical situations such as shopping, returns, apps, and websites.

客服 is short for 客户服务 and usually means customer service or customer support.

Depending on context, it can refer to:

• the customer service department
• a customer service representative
• customer support staff in general

Chinese often shortens common expressions, so learners will see 客服 a lot in real life.

Examples:

• 联系客服 = contact customer service
• 客服说... = customer service said...
• 问一下客服 = ask customer service

才 is very important here. It emphasizes that the result happens only then, after the condition is met.

• 我们才知道 = only then do we know
• 我们才知道怎么退货 = only then can we know how to return the goods

Without 才, the sentence would sound less complete and much less natural in this pattern.

In the structure 只有...才..., the two words work together. Learners should usually treat them as a pair.

Usually no, not in this sentence.

• 才 fits 只有 and expresses only then
• 就 often suggests then / right away / as soon as

So:

• 只有...才... = only if..., then...
• 只要...就... = as long as..., then...

That is a different meaning.

Compare:

• 只有先联系客服，我们才知道怎么退货。 = Only if we contact customer service first can we know how to return it.

• 只要先联系客服，我们就知道怎么退货。 = As long as we contact customer service first, we’ll know how to return it.

The second version is less exclusive. It does not stress this is the only way as strongly.

Yes, literally it is something like how return goods, but in natural English it means:

• how to return the goods
• what the return process is
• how a return should be done

In Chinese, 怎么 + verb often means how to do something.

Examples:

• 怎么做 = how to do it / how to make it
• 怎么去 = how to get there
• 怎么退货 = how to return the goods

So this is a very useful pattern to learn.

It could, but 怎么 is more common in everyday speech.

• 怎么退货 = natural, conversational
• 如何退货 = more formal, written, or official

If this were on a website, in a policy document, or in very formal customer support language, 如何退货 might appear. But in ordinary spoken Mandarin, 怎么 is usually the more natural choice.

Because this sentence sounds like a general condition or rule, not a completed event.

• 只有先联系客服，我们才知道怎么退货。 = This is the procedure / this is what must happen.

If you add 了, the sentence sounds more like a specific situation that actually happened:

• 只有先联系了客服，我们才知道怎么退货。 = Only after we had contacted customer service did we find out how to return it.

So the version without 了 is better for expressing a general requirement or process.

退货 is a general verb meaning to return goods / make a return. It does not have to specify exactly how many items.

Chinese often leaves this kind of thing general unless the exact item matters.

So 退货 can mean:

• return an item
• return some goods
• process a return

If you want to be more specific, you could say things like:

• 退这个商品 = return this product
• 退这件衣服 = return this piece of clothing

But in a general sentence about return procedures, 退货 is very natural.

Sometimes yes, if the context already makes the subject obvious.

For example, in conversation, someone might simply say:

• 只有先联系客服，才知道怎么退货。

This still sounds natural and means something like Only by contacting customer service first can one know how to return it.

However, including 我们 makes the subject clear:

• we are the ones who need to know how to return it

Chinese often omits subjects when they are obvious, but keeping them can make the sentence easier for learners to understand.

A little, but the standard learner-friendly pattern is:

• 只有 + condition, + subject + 才 + result

So the most straightforward version is:

• 只有先联系客服，我们才知道怎么退货。

You may also see variations, but changing the order too much can make the sentence sound less natural or can shift the emphasis.

For learning purposes, it is safest to remember this pattern as a fixed frame:

• 只有...，...才...

The comma separates the condition from the main result.

• 只有先联系客服， = only if we contact customer service first
• 我们才知道怎么退货。 = only then do we know how to return it

In speech, there is usually a pause there too. So the comma helps show the structure clearly.

It is especially useful in sentences with 只有...才..., because it makes the logic easier to see.

It can suggest both, depending on context.

知道怎么退货 can mean:

• know how to return it
• find out how to return it
• learn what the return procedure is

In many real situations, the idea is not just abstract knowledge. It often means we can only learn the return process after contacting customer service first.

So the English translation may vary a little depending on context, but the Chinese structure stays the same.