zoom R8 audacity 3.0.0 cant hear mic when recording

my setup is (new user to audacity)

windows 10 laptop
zoom r8 unit connected via usd to laptop.
rode mic connected to zoom unit.
zoom directed to USB : works ok.

if you see my image the top track is the backing track
the 2nd track is my instrumental through the mic.

problem : when i play i can hear the track ok through headphones via the laptop, when i record through mic on top of the backingtrack , i cant hear the mic through headphones - only the backing track.
when i finish recording and playback i can hear everything OK - but i am having to guess on how close i get to the mic and thats not good.

i set the speakers to zoom but when i pull out the headphones from the earphone jack the sound just comes out of the laptop.
if i plug my headphones into the zoom i hear only the mic

Turn on [u]Software Playthrough[/u].

thanks doug - i got hopeful there - plugged the headphones into the zoom instead of the laptop and set the audacitiy > playthrough to ON (it was OFF) - can hear the mic and the backing track BUT when i go an press the RECORD i get this -9999 err. i have looked it up on the manual and it could be many things - drivers etc, and i may never solve it.

just one other thing - if i put the playthrough ON and leave the headphone in the lap top i get sound from the mic and backing track BUT there is a massive lag on the mic part - ive tried setting the latency compensation from defult setting -130 to -170 after i did one of those lag timing tests on a rhythm track but no matter how much i adjust it makes NO differnce to the result. you just dont hear the lag getting any shorter.

basically , i’m a musician trying to put a demo together - ive spent all weekend trying to make this work and i cant - i may have to give up as i’m just not able to spend hours and hours on this. i’m just not technical enough.

some people are saying on the internet that you will never be able to solve this lag as it comes from the usb wire to the zoom.
it just seems so disappointing that we cant even make a recording over a backing track with all this technology.
my fostex 4 track did it so well in the 80’s. i just dont have it anymore sadly.

any last ideas appreciated .