cheapie head unit install

so i bought a ebay 9 inch head unit . last time i did this all you could get was a radio with tape deck , thigs have changed a bit since then .
It's got 4G ram with 32G memory ,reverse cam gps etc; but pretty much no install documentation . so here goes . First up a pic of the new head unit beside the old radio. the new one comes with a new trim surrounds .
Attachment 85902
then a pic of the bluetooth mic , gps antennae and wifi antennae.
Attachment 85903
first question . the bluetooth mic wire is about 2.5 meters long , and , i only need about 500mm . can i cut and solder it shorter , or is that a nono , because maybe it is a centre wire with a wire sheath , or would it just be 2 wires .
Next question . where would be the best place to put the gps and wifi antennaes . If you see the pic's below you will see i am holding them up near the top corners because the wires are not long enough to move them closer to the centre . but i will put one either side. .Attachment 85904
Attachment 85905

I have installed a similar unit on my 105 a couple of years ago. About the MIC, I wouldn't bother just keeping the excess wire tidy up and strapped with a nylon strap under the dash. About the antennae, if you want to have them exposed, the windscreen or on top of the dash are good options. In my case I have left both under the dash and it worked the same (I've tested). So, at the end, its just about the looks.

Thanks @brazilian Y60 . I've already got bit of a rats nest of wiring happening under the dash and don't want to make it worse . cutting and soldering is easy if it is only 2 wires , but if the mic has a outer shield wire it might not be so successful . i am supprised about the gps and wifi antennae then . i did find in the past , when i first got my samsung 7" tab that i have ozi explorer maps on , that it worked better on top of the dash than lower down in front of the dash , when i was looking for a place to put it . I might still fit the antennae on the windscreen as i only want to fit it once and not have to do it again if i have issues with it

The mic cable will definitely be shielded and could be difficult to re-connect. The centre wire is quite fine so unless you are experienced in delicate soldering, just leave it bunched up as previously suggested.
The antennae can be successfully installed under the dash as long as it is not covered by anything metal. The plastic dash will not impede either signal. The GPS one needs nothing metal between it and the sky.

Excellent , thanks for that @Brissieboy . i'll just bunddle the mic wire up and leave it at that then , and i will have a look under the dash for a good spot to put the antennae .

ok . i have pretty much finnished the installation of this unit . looks good . radio reception is much better ( in garage , garage door closed , aerial half up , perfect reception . original one was just static . ) got auto androidauto working but decided it wasn't for me . got reverse cam working but still have to fit it to rear . the facia pannel needed a bit of work to get it to fit neatly but it turned out good in the end .