Solution

at the northern end of the north-south road east of the city, open gates,n,

n,n,n,e,e,e,e,enter house,u,s,search books {in the library}, you'll find a

book about guineapigs, read it and you'll know what they like to eat,go out,

in the northern part of this area there is a wall, loosen mortar,push stone,

until you can go north, here you have to 'search' for the certain thing the

guineapigs like most and get two items of this kind, if it is grass, go to

the place in the middle of this area and 'gather grass' {two times}, go back

to the house,n,d,kill cat,drop <food>, wait till the pig come forth and go

up to the girl {in the first floor}, but wait until the pig follows you