C, mon all is not lost,
With a little thinking and not much skill both boards can be fixed.
Both boards have a t slot kind of arrangement going on,
Even with only hacksaw and angle grinder skills it would not be hard to make a t shaped brass slug with an 8 mm tapped hole to fit all new mast base joins.
If what I said didn't make sense I'm sure the neighbour with tools will be able to do this over a couple beers.
Just wont be adjustable while your riding. Unless your racing it wont matter , all the way back

The rubber bendy thing needs to be replaced,
Go to a windsurf shop with your mast and get a second hand mast ext and base , $ 40 tops.
ps , if u can get a lesson ( one will do ), that's the best $ 50.00 you'll spend.