5. We think your draft contract needs some modification.
我方認為貴方草擬的合同需要做一些修改。
還能這樣說：
We feel that the contract you made needs to be revised partly.
We think we should modify the contract in some respects.
應用解析：
make out a draft of 起草；
on draft 桶裝的，隨時可以從桶里汲出的

6. Once a contract is signed, it has legal effect.
合同一旦簽署即具有法律效力。
還能這樣說：
This contract will come into force as soon as it signed by two parties.
A contract become valid immediately after it is signed.
應用解析：
be in force 生效，有效；
be forced into 被迫；
bring into force 使生效，實施

7. The buyer has the option of canceling the contract.
買主有權撤銷合同。
還能這樣說：
The buyer has the right to declare that the contract is null and void.
The buyer has the final say on repealing the contract.
應用解析：
at sb.'s option 隨某人的意；
keep (leave) one's options open 暫不表態，留有回旋余地

8. We can get the contract finalized now.
現在我們可以簽訂合同了。
還能這樣說：
We can sign the contract now.
It's time to reach the agreement now.
應用解析：
finalize the design 定型；
finalize model 最終確定模型