One cannot divide inheritance at night. What exactly this statement means is explained by the gemara, based on a braita and a statement made by Rav Yehuda and Rav Hisda. The statement of Rav Yehuda relates to the concept discussed in other places that a witness can’t also function as a judge. What exactly is meant by a witness is a subject of debate among the commentaries. When one makes a kinyan, there is a certain timeframe in which one side can change their minds. What that timeframe is is a subject of debate between Rabba and Rav Yosef. What type of kinyan the gemara is referring to is debated by the commentaries. Why is the mishna repeating cases that can be inferred from the previous section? Rabbi Yochanan says in the name of Rabbi Yehuda ben Shimon that a woman inherits from her son. However Rabbi Yochanan questions that this goes against the mishna. Rabbi Yehuda rejects our mishna and says that he doesn’t know who wrote our mishna!