1)
Why does it say "Asher Shamanu va'Neda'em"?
1.
Radak: The words that I will say, we heard them from earlier [ancestors]; we know them also from what is written in the Torah of Moshe Rabbeinu.
2.
Malbim: What he tells of Keri'as Yam Suf, the manna, the Slav, Hashem descending on Har Sinai
2)
Why does it say "Avoseinu Sipru Lanu"?
1.
Radak: Our fathers would tell us only Emes.
2.
Malbim: Our father told us that these stories are true.
