"But I do not know how to do it with a knife!"
Translation:Já to ale nožem udělat neumím!
In this case the instrumental case requires "s", not "z", but it is much better without any preposition (just nožem without s or z).
True, but if you phrase it like Tom, it's more about the knowledge of the way of doing something rather than the ability to do it. And I don't think you can say "neumím jak to udělat", only "nevím jak to udělat".
thanks. Does the "ale" count, so it has to be "Já to ale ...", or is "Ale já to ..." or even "Já ale to ..." possible?
thanks a lot. I'm still working on developing an intuition for this, but existing rules definitely are helpful for me.