Speedometer and fuel gauge issues

Hey everyone !

Getting right into it,

My hyo GT250 (naked) has issues with the speedometer and fuel gauge. The speedometer is wrong showing a out 10km too fast than actual speed sometimes more. I know motorcycle speedos are always a bit off but it was never that much before.

My fuel gauge, is also wrong. I’ll fill up and the needle will just move bellow empty and then freely go up and down whenever until I’m at about half tank where it will show half tank and stay there for a while then when in low it will go low, then I fill up and it happens again.

I asked my mechanics about at my last service and they said it’s got to do with the electrical stuff on the inside of the bike which happens when it gets old. (2006 bike)

The speedo got replaced less than half a year ago because someone thought it be nice to smash into it and break the old one.

Any suggestions how I can fix these issue ?!?

Thanks in advance !!