Questions & Answers about לא הבחנתי בכתם על החולצה עד שחזרתי הביתה.
The ending ־תי marks first-person singular past tense in Hebrew: I.
So:
- הבחנתי = I noticed / I discerned
- חזרתי = I returned / I came back
A useful point: in the first person, Hebrew does not distinguish masculine and feminine in the past tense. A man and a woman would both say הבחנתי and חזרתי.
Hebrew does not use English-style do-support.
In English, you say I did not notice.
In Hebrew, you simply put לא before the verb:
- הבחנתי = I noticed
- לא הבחנתי = I didn’t notice
So לא is the normal way to negate a past-tense verb here.