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the keyboard works just like any keyboard, by creating a short-circuit between two lines in a grid, but if it doesn't work don't really expect to repair it unless the problem is really simple to solve.
you could try to expose the contacts of those keys, on the pcb and the key and try to clean them, make sure you dry them properly before assembling it again, don't scratch the contacts, clean them gently and don't rub them too much.