Is it permissible for a company with investors who share in profits and capital for a limited period, to open a new branch wholly owned by it from its net profits, without harming the first branch or breaking prices?

There is no impediment for the company owners to trade with their private funds in an activity similar to the Mudarabah (definition) activity with others' funds without their knowledge. However, if the Mudarabah contract with the investors was based on a percentage of the capital, not the profit, or if it included a condition guaranteeing the capital, then this Mudarabah contract is invalid.