I know that there are a million thread like this already, but I'm worried that my bonzai is Dead/Dying, I've attached a picture of it.

Basically the leaves are almost all brown at this stage, its my first plant a Zanthorxylum, my mum bought it for my birthday at my request, but I obviously don't have a green thumb :(

I think i've been over watering it and leaving it on the window sill during a heat wave probably wasn't a very good idea either -.-

Is there anyway I can save it? or should i recycle it and start over when I'm better prepared?

Thanks