(1) Any amount that is invested in business, its account is maintained clearly, and on the maturity of time, the profit and loss is divided after calculation among the shareholders as per their capital amount, it is called Shirkah (partnership), which is a lawful mode of business.
(2) In the same way, if someone is given money as muzarabah and that person starts business with that money and maintains the calculation of profit and loss clearly, then as per the muzarabah rules (whose detail is written in Bahishti Zewar and other Fiqh Books), both will share the profit and loss. This form of muzarabah is lawful too when its conditions are maintained. In case of loss in muzarabah, investor will bear the loss of wealth while the worker will bear the loss of labour.
It is interest to fix any particular amount in partnership or muzarabah for any person. It shall be interest though this amount is fixed more or less due to any reason; since the actual profit or loss cannot verified without maintaining the account and the partner shall be content only after observing the account and calculation details.
Whatever detail you have written for business it does not explain the complete situation. Also, it is not clear what settlement was reached in case of loss? Here, you did not make it clear if any of these situations happens i.e. the loss means all the following situations i.e. more or less profit, or there was no profit at all, or complete capital amount or its some part was lost, then what was settled between you? Hence, this dealing seems to be based on interest.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband