Secondary Dominants and 2,5,1s

[Adde]

Hey people. I'm struggling with some music theory from UNI, and since I live in a student apartment I need to create certain results within 5 days, or I lose this apartment, which would be really bad in many ways. But here is the thing - I can't seem to figure out certain things no matter how much I try to wrap my head around them. So here I am, asking the people of "KVRaudio" for help.

The first assignment I have to finish, is the one attached down below.
"Harmonize the song with either 2 5 1s or secondary dominants - exchange the question marks for chords.

This is as far as I've gotten and then I got lost:
G - Gmaj7 - Am7 - D7 (or does G fit better, rather than D7?)
G -

I don't understand what do to as C is in the midst. I've been trying forever to figure this out, but I'm going to assume that I lack knowledge that I can't seem to find in a way I understand here online.

Can anybody help me? I would more than appreciate this.

Thanks so much in advance,

With kind regards,

Andreas

[soulata]

G Gmaj7 Am7 D7
G G7 C E7
Am Am7 D7 Em A7