So money is considered as plural ? Does the same count for trash ? Takataka zangu ?
Nope. I guess you got misled by seeing "singular" and "plural"
nyumba yangu = my house
nyumba zangu = my houses
nyumba yetu = our house
nyumba zetu = our houses
You will hear pesa in daily speech. Fedha is somewhat more official, and you would probably hear that in cases where English uses 'funds'. All Tanzanian banknotes are 'signed' by Waziri wa fedha, i.e. Minister of Finance, and 'Gavana' which means Governor (governor of what I don't know:)
Btw: the word fedha originally means silver