These are all difficult Japanese expressions to translate into other languages.
「あの人は虫がいいね」 He/She thinks only about his/her own benefits.
「足が出てしまった」 I have run over the budget.
「気の置けない友達」my close friend I don't have to take so much care of
「猫をかぶる」 He pretends to be a quiet person in public.
I don't think these are good translations, but maybe they are helpful to you to some extent.