Is permissible to buy/sell with non-Muslim?
Yes buying/selling for a Muslim with non-Muslim is permissible as regards what is lawful.
I work at a company that provides cash advances of 800 dinars, 1000 dinars, or 1200 dinars, depending on the employee’s years of service. An administrative fee of 40 dinars is deducted from the amount in the first month, and the remaining amount is repaid in installments. What is the ruling on this, knowing that the deducted amount (40 dinars) is fixed?
We fear that the deducted amount may be a means of circumventing interest (Riba). If the deducted amount is equal to or less than the actual administrative expenses, then there is no issue, as some scholars permit the borrower to bear the costs of documenting and managing the loan. However, piety suggests refraining from taking this loan under these conditions, as dealing with private individuals and companies is not the same as dealing with the state, which spends from the public treasury. And Allah Knows Best.
What is permissible for the husband to do as far as having sex with his wife is concerned?
The couple are free to enjoy each other sexually provided that they don`t do it during menses. It is also forbidden for the husband to enjoy the wife from her anus.
Is it permissible to offer Salah (prayer) on behalf of the sick who is on his/her death bed, and is incapable of offering it?
It`s impermissible to offer Salah on behalf of the sick, or the dead.