Rule 1: 1. لَمْ in conversation
In speech and prose لَمْ + jussive is the normal way to say did not: لَمْ تَجِدِ الْوَرَقَةَ she did not find the paper. With the question hamza it becomes أَلَمْ did … not?, which often expects the answer yes: أَلَمْ تَسْمَعِي كَلَامِي؟ did you not hear what I said? Remember the helping kasra before the article and before any other hamzat al-waṣl: لَمْ تَذْكُرِ الشَّيْءَ الرَّابِعَ.
لَمْ تَجِدْ سُعَادُ الْوَرَقَةَ فِي السَّلَّةِ.
lam tajid suʿādu l-waraqata fī s-sallati
Suʿād did not find the paper in the basket.
لَمْ يَزِنِ الْبَائِعُ السَّمَكَ.
lam yazini l-bāʾiʿu s-samaka
The seller did not weigh the fish.
يَزِنُ loses the و of وَزَنَ; the jussive is يَزِنْ, with kasra before the article.
أَلَمْ تَدْفَعُوا ثَمَنَ اللَّحْمِ؟
a-lam tadfaʿū thamana l-laḥmi
Did you not pay for the meat?
لَمْ نَشْتَرِ فَاكِهَةً الْيَوْمَ.
lam nashtari fākihatani l-yawma
We did not buy fruit today.
The imperfect نَشْتَرِي ends in -ī; in the jussive the ī is cut off: نَشْتَرِ. Learn this one form for now.