Is the method of dealing with the aforementioned marketing company, which requires purchasing goods from a specific company to own them and then marketing them for cash or on credit for a specified profit, considered permissible (halal)?

It is permissible to appoint a marketing company to buy and sell certain goods through Murabahah (definition) if the company is trustworthy and actually buys and sells the goods. However, it is not permissible if the matter is merely a trick to conceal usury, whereby the company returns the amount with a specified interest. One must be cautious of companies that hide behind usurious tricks, especially those found online.