「合作」最簡單的講法是work together,還有一個實用的片語也有合作的意思,是team up with。
★ (正確)I look forward to working with you again.
期待與您再次合作。
★ (錯誤)I hope we can have better cooperation in the future.
★ He didn't want to team up with anybody.
他不想與任何人合作。