Certain keys not working on A1314 keyboard for iMac 2011

Hello, I have an imac 2011. I got a keyboard model a1314 with it. But it broke. I had another one of the same model, but now I can't use certain keys h,j,k,m,i,o,u. I heard that I should press alt 5 times but it doesn't help. Please help.

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