Is keeping money in and taking profits from the Islamic Bank lawful?
If Allah Wills this is lawful, because they stipulate on theselves to work in accordance to the guidlines of Islamic Law. And Alalh Knows Best.
Is it permissible for a woman to use a contraceptive without telling her husband although he wants to have as many children as possible and she can`t care for them?
All perfect praise be to Allah, the Lord of the Worlds, may His Blessings and Peace be upon our Prophet Mohammad and upon all his family and companions.
If the pregnancy is harmful to the woman, it is permissible for her to use a contraceptive; however, this has to be backed by a medical report from a God-fearing doctor. In addition, you had better inform your of what you are doing to avoid dispute. And Allah The Almighty Knows Best.
Is permissible to buy/sell with non-Muslim?
Yes buying/selling for a Muslim with non-Muslim is permissible as regards what is lawful.
How long is the` Iddah (waiting period) of a divorced woman?
The waiting period (iddah) of a divorced woman who is pregnant is until she gives birth. If she is of menstruating age, her waiting period is three menstrual cycles. If she does not menstruate, her waiting period is three months. And Allah Knows Best.