Stuck on which screws I need

Same boat as you, it doesn't look like it is included in the assembly manual in the google drive.

I bought different screws, and I nearly got it together... let me sum them up:

1 x m3x16, conical head for the chamber

1 x m3x8 conical head for the chamber

2 x m4x16 for the handgrip to the body

2 x m4 nuts

2 x m3 x 16 (flat head) for the lens ring mount

2 x m3 x 14 (flat head) for the phone clamp

2 x m3 washers (flat) for the phone clamp

6 x m3 nuts

then you'll need three self tapping screws (for the handgrip) 3 x 5mm

I used hexagon heads for all, I like the look, and I have bought a hexagon bit for the m3 bolts for the phone clasp, and the bit fits nicely in the top of the handgrip, so you can always tighten the screws while 'in the field'

hope this helps you!