There is always more to say, but I answered this query in the course of a longer essay about Engels's Manchester years a while back. Engels was not in charge of the business he was sent to Manchester to join - a cotton thread factory. It was majority-owned, and run, by his father's business partner, Peter Ermen.

Ermen suspected that the younger Engels had been sent to spy on him, so he refused to place him in positions where he had much responsibility or participated in strategic decision-making. Engels was largely restricted to mundane clerical duties in what he called "the bitch business", spending 20 years maintaining an extensive correspondence with suppliers and clients, while systematically raiding Ermen's petty cash box for some of the funds he passed on to help support his colleague Marx.

I have written in much more detail about Engels's time in Manchester, here. You might like to review that while you wait for additional answers to your question.