the gate of their city
It was common for leaders to meet at the city gate to make official decisions.
"Jacob, his sons, and the people of Israel"
peace with us
Here "us" includes Hamor, his son and all the people they spoke with at the city gate. (See: rc://en/ta/man/translate/figs-inclusive)
let them live in the land and trade in it
"let them live and trade in the land"
for, really, the land is large enough for them
Shechem uses the word "really" to add emphasis to his statement. "because, certainly, the land is large enough for them" or "because, indeed, there is plenty of land for them"
take their daughters ... give them our daughters
This refers to marriages between the women of one group and the men of the other group. See how you translated similar phrases in Genesis 34:9.