gyeyak jogeoni bakkwieoseo geu iyagineun dasi haeya haeyo.

계약 means contract, and 조건 means condition(s) or terms depending on context.

So 계약 조건 is most naturally understood as contract terms or the conditions of the contract in English. Even though 조건 literally looks like condition, in business/legal contexts English usually prefers terms.

This is the difference between an intransitive and transitive verb.

• 바뀌다 = to be changed, to change on its own
• 바꾸다 = to change something

So:

• 조건이 바뀌어서 = because the terms changed
• 조건을 바꿔서 = because someone changed the terms

In your sentence, the focus is on the fact that the contract terms ended up changed, not on who changed them, so 바뀌어서 is the natural choice.

Here 바뀌어서 means because (it) changed.

The ending -아서/-어서 often connects two clauses and can express:

• sequence: did A and then B
• reason/cause: because A, B

In this sentence, it is clearly the reason meaning:

• 계약 조건이 바뀌어서
  = because the contract terms changed

So the whole sentence is basically:

• Because the contract terms changed, we have to talk about that again.

이/가 marks the subject, while 은/는 marks the topic or contrast.

Here 조건이 바뀌어서 presents the contract terms as the thing that changed:

• 조건이 바뀌다 = the terms change

Using 이/가 is the most neutral and natural way to say that.

If you said 조건은 바뀌어서, it would sound more contrastive, like:

• As for the terms, they changed...
• or implying comparison with something else

That is possible in some contexts, but the plain sentence usually uses 조건이.

The 는 here marks 그 이야기 as the topic, and it can also add a slight sense of contrast or as for that matter.

So 그 이야기는 다시 해야 해요 feels like:

• As for that discussion, we need to do it again
• That part needs to be discussed again

This often sounds natural in Korean because 은/는 helps shift attention to a topic already known in the conversation.

If you said 그 이야기를 다시 해야 해요, that would also be possible, but it feels a bit more directly object-focused: we have to talk about that again.

With 그 이야기는, the nuance is slightly more like that topic/discussion, we need to revisit it.

Literally, 이야기 can mean story or talk/discussion. In this sentence, it does not mean a story in the literary sense.

Here 그 이야기 means something like:

• that discussion
• that matter
• what we talked about
• that issue

So in business or practical conversation, 이야기하다 and 이야기 often refer to discussing a topic, not telling a story.

Korean often uses 하다 with a noun where English would use a more specific verb.

Here:

• 이야기하다 = to talk, to discuss
• 이야기를 하다 = literally to do a talk/discussion

So 그 이야기는 다시 해야 해요 literally looks like as for that discussion, we have to do it again, but natural English is:

• We need to talk about that again
• We need to discuss that again

This noun + 하다 pattern is extremely common in Korean.

-아/어야 하다 means have to, must, or need to.

So 다시 해야 해요 means:

• have to do it again
• need to do it again

It expresses obligation or necessity, but in -해요 form it sounds polite and fairly neutral, not overly harsh.

Compare:

• 다시 해야 해요 = polite, normal conversation
• 다시 해야 합니다 = more formal
• 다시 해야 돼요 = more conversational, common in speech

Korean usually puts important verbs at the end of clauses.

This sentence is structured like:

• 계약 조건이 바뀌어서 = because the contract terms changed
• 그 이야기는 = as for that discussion
• 다시 해야 해요 = must do again

So Korean naturally builds up the context first and gives the main action at the end.

A very literal breakdown would be:

• Contract terms changed-because, that discussion-topic, again must-do.

This is completely normal Korean word order.

Sometimes yes, depending on context, but not always.

The literal meaning is closer to:

• We need to talk about that again
• We need to discuss that again

If the topic is specifically a contract negotiation, then in natural English you might say:

• We need to renegotiate that
• We need to go over that again

But Korean itself does not explicitly say renegotiate. It just says the discussion needs to happen again because the contract terms changed.

Yes. 얘기 is a very common shortened form of 이야기, especially in speech.

• 이야기 = full form
• 얘기 = casual spoken contraction

In writing, especially in a sentence that is polite and somewhat businesslike, 이야기 is often preferred.

So:

• 그 이야기는 다시 해야 해요 = a bit more neutral/polite
• 그 얘기는 다시 해야 해요 = very natural in conversation, slightly more casual

Both are common.

Yes. 변경되다 is a more formal, business-like word meaning to be changed.

So:

• 계약 조건이 바뀌어서 = natural, everyday
• 계약 조건이 변경돼서 = more formal, business/document style

Both are correct, but 바뀌어서 sounds more conversational.

Likewise, a more formal full sentence could be:

• 계약 조건이 변경돼서 그 이야기는 다시 해야 합니다.

That would sound more appropriate in a formal workplace or official setting.