some wired Keyboard keys stopped working (8 i k , (comma) do not work)

I'd guess it is now faulty. That set of keys in a line suggests it is the scanning hardware, rather than individually worn keys. Disappointing for an expensive apple one, unless it is old.

Suggest contacting apple if in warranty or fairly new. Otherwise you probably have to replace it, though probably worth trying in another computer first just to rule out some weird software issue. That is pretty unlikely to be the case though.

Unfortunately that keyboard cannot be repaired. It will need replaced. There are multiple vendors that sell USB keyboards for Macs.

Keyboard make and model?

What computer is it attached to and what OS is it running?