On your stats you have a BMR of 1514 n an ideal weight of 63 with a range of 53 to 72. So assuming you have excess body fat 4 kg target is ok.
I'd suggest you up your eating calories up to 1,500 not too far from your present level as eating below your BMR for extented periods could slow down your metabolism making it harder to lose weight. Try making your 45 min walk a run n add on 15 min a day of light weights. A set of dumbells done at home should be enough to up your metabolism enough to lose 1/2 kg a week without making it too much of an effort.
Thanks for the reply! I'll try out those tips :)