Already fired and then defending in an assault

[plloyd1010]

I realise the rule says a unit defending in an assualt does not activate and is NOT marked with a fired/moved
but if the already fired do they get to fire again in the assualt?

Yes, they may fire defensively in assault combat. They would be unable to initiate an assault until the next turn.
 

In this instance its a German HMG
cant they use full fire when defending? and first fire (as dug in?0 or do the HMG restrictions apply when they are the assault defender?

The HMG's defensive would be at full strength. The 1/2 strength condition applies when initiating an assault and there is no accompanying infantry in that assault.