What is the ruling on the 4% interest on a loan granted by the Libyan Foreign Bank for investment in Niger, and is it permissible to continue with this investment?

A loan that benefits the lender is usury (riba). The lender is only entitled to the principal amount borrowed, without the stipulated interest. The questioner is not permitted to pay this interest unless compelled to do so, and failure to pay would result in harm. As for continuing with the company founded on this borrowed money, there is no sin in that, because usury pertains to the interest, not the principal amount, especially since the borrower was unaware of the usurious interest at the time of the contract. However, one must not return to such borrowing after learning of its prohibition.