1) In hierdie sin moet ek 'aan' gebruik of kan ek ook 'op' gebruik ? Is een beter as die ander?

Well in this context "aan" translates to "on" meaning it is on your righthand which is correct but in this context "op" translate to "on top of" meaning the post office is on top of your right hand which is clearly not what you mean. O no in this context you can only use "aan".

"en dan sal jy die postkantoor aan/op jou regterhand vind"

2) What beteken die word "tuisnywerheid" ?

Is dit wat mense in Amerika noem 'n "Hardware store" ?

No it is a place where bakers mainly take their cakes to be sold on behalf of them. People very rarely use the word I had to ask my mom what it means.

Baie dankie vir jou help :)
My pleasure ask anytime