Used after a verb ...   过

过, a particle, is used after a verb to indicate the completion of an action or an action once happened or a state once existed.

Subj. + V + 过+ NP

Example:
1. 我和中方公司已经商谈过这件事了。(Completion)
I have already discussed this issue with the Chinese company.
2. 我去过北京的自由市场。(Experience)
I have been to the free market in Beijing before.
3. 这种服装再美国流行过。 (A state once happened)
This type of dress used to be popular in the USA.

Substitutive drills:
 大卫和玛丽都逛过中国的自由市场。
 美方总裁去过中国。
 王小姐去年翻译过这个合同。
 美国公司跟中国公司讨论过贸易合同的问题。
 张董事还没有看过会议记录。