why isn't it:ביום שישי החוזה שלי נגמר?
Why wouldn't "...my contract is finished" or "I will finish my contract" be acceptable? It's actually more correct in English.
Best would be "the contract ends". The Hebrew does not indicate the subject "I" doing the finishing.
בְּיוֹם שִׁישִּׁי נִגְמַר לִי הַחוֹזֶה.
This is not written well in English. It should be: my contract is finished OR will be finished.
...‘my contract finishes’? Is my contract a machine or a sentient being that finishes an action?
חוזה זכר או נקבה?
The past tense should also be accepted — e.g. “On Friday my contract was completed.” — since “נגמר” could be either ”נִגְמָר” or ”נִגְמַר”.