Hi Nana
for rules of arabic plurals I have this link for you I hope it would help you:
http://www.hmaxos.com/Arabic%20Plural%20System.pdf
FRIEND sadiq / sadiqah > asdiqaa
man / woman rajul/ mar'ah > rijaal/ nisaa'
star najmah > nojoum
sir/ madam sayidi/ sayidati > sadati/ sayidati
boy/ girl walad/ bent > awlaad/ banat
house manzel >manazel
car sayyarah > sayyaraat
Brazilian brazili/ braziliah > albraziliaat
Arab arabi /arabiah > arab
policeman shorti/ shortia > shortah
policeman bolesi/ blesiah > boleese
table tawela > tawelaat
chair korsi > karasey
family 3a2ilah > 3a2ilaat
music musiqa > musiqa
city madina > mudon
country dawlah > dowal
nationality jensiah > jensiaat
heart qalb > qoloub
son/ daughter ebn / ebnah > abnaa'/ banaat
kid/s - child- children tefl / teflah > atfaal
beautiful / handsome jameel > jameeloun
good / bad (person) tayeb/ shereer > tayeboun/ sherreeroun
good/ bad (things) jayed/ ghair jaid > jayyedoun/ ghair jayyedoun
nice / not nice (in Brazil we say simpático/a) tayeb > tayeboun
interesting mouhim > mouhimmoun
boring mumil > mumilloun
big/ small kabeer / sagheer > kebaar / seghaar
tall/ short taweel/ kaseer > tewaal / kesaar
young/ old shaab/ shaik > shabaab / shoyoukh
happy/ sad sa'eed / hazeen > so'adaa' / 7azeenoun
some of the singular words have more than one plural, that's why you need to have a look at the link I gave you.