The red connector, white grey green purple wires, and the same colours with a black tracer - that is the amplified speakers out, plain colour +ve with black tracer being the corresponding -ve. Those should be connected to the corresponding wires from the back of the head unit beside the red 10a fuse, but I don't know how that would play with the Harmon Kardon amp? Ordinarily other in car systems with an OE amplifier use pre-outs (unamplified audio outputs) which are the phono sockets at the right hand side. That one phone you have connected is the one speaker you have or had working. If you follow the wire from the phono plug it goes to the grey white green and purple wires I mentioned previously.
You can keep the headunit, and get it for working for not a lot of money, but you're going to have to do some wiring, which, with your limited skills, no soldering equipment or skills, is going to be a mess of bullet connectors / coco blocks / scotch locks, but it can be made to work., just the wiring isn't going to be pretty.
Before you fitted the new loom, the blue wire from the back left of the head unit was connected to something, that connection needs reestablished. Then you're going to need find a way of connecting the green grey purple white wires, into phono connectors and plugging them into the back of the head unit. Without the ability to solder, you are either going to have to find some phono leads with the plug wired and two wiring tails, or an old set of speaker leads with twin wires rather than coaxial cable. or maybe these:
https://www.ebay.co.uk/itm/4pcs-New...905852?hash=item5daa498e7c:g:-7kAAOSw4yte3gtg
I don't have time to do the online shopping for everything you are going to need to do this without soldering, just now, but it might not be all that expensive to get a local car audio / autospark to wire this up for you. Have a phone around, and tell them you are
"looking for a price to get the eight speaker wires from an iso harness adapter connected up to for RCA / Phono connectors to plug into the back of the head unit." see what they say, and get back to us. And or you could look for phono / ca leads you can see with twin wires coming out of them rather than single coaxial cable.
If I get a chance later, I'll have a better look online for you...
Catch you later - Jay