Why does the Torah write "Yevi'ehah", and not "Yavi"?
Ramban, Moshav Zekenim citing the Rosh: Sometimes the Torah first mentions the object generally, and then describes it in detail. 1
Ramban (according to Kabalah): See Ramban.
Why did Moshe see fit to repeat all the aspects of the Mishkan (albeit in general terms) to the people?
Ramban, Moshav Zekenim: Moshe already told them about the Mishkan in detail (in Terumah from Shemos 24:2) and in general terms (in Ki Sissa, from Shemos 31:7). Now that the time to donate had arrived, he gave them a broad picture of all that was required, to prompt them to donate generously. 1
What is "Nediv Libo"?
Rashi: Since his heart makes him volunteer, he is called Nediv Lev. 1
Moshav Zekenim: Nediv describes the person. 2 "Lev" refers to the intellect, and not the physical organ.
Why must it say "Kechu me'Itchem"? From whom else could they take?!
Moshav Zekenim: It must totally belong to them, but not something stolen.