至于你的问题:
1. The workload definitely is too much for one person.
谁的定义?你的,还是公司的?建议与给你派活的人谈一下,看看公司的期待值。
鞭打快牛,派活的人考虑的是把活干出来,而不是合理负担。如果你的工作量超过了期待值,你应该让派活的人知道。(职场沟通第一定律:你不说,他怎么知道。)
2. Should I work for afterhours without pay? How to negotiate for the afterhour salary?
No.
“I will work tonight to meet the deadline at 7:30 am tomorrow morning. The rate of OT of the company is XX/hr. and I need Y hours to finish the work. How do you want me to file OT?/Is that agreeble with you?“ (后面一句比较柔和,但会引起讨价还价。我会选择前面一句。因为合同工按小时付钱,加班费是天经地义的。)
3. How many hours do people usually fill in the time card (7.5 h per day or 8 h per day)?
查公司规定或合同规定。
题外的话:放弃自己应得的报酬和建立自己的信誉是两回事,你要建立的信誉是事情做的好,而不是廉价的劳动力。廉价劳动力和质量低往往被混为一谈,即使不是事实。