Are the partners entitled to demand the money they gave me for investment, knowing that I did not take it for myself and that I also lost my own money in the same business?

It is not permissible to guarantee the capital of a Mudarabah (partnership) unless there is transgression or negligence, because the عامل (Mudarib/agent) is an أمين (trustee). However, if the agent is negligent or transgresses, then the guarantee becomes valid, and the aggrieved party has the right to demand their money. Scholars have differed regarding the extent of the right of the rightful owner to demand from the guarantor: is it absolute, or only when it is impossible to demand from the guaranteed party? It is not permissible to take a fee for the guarantee.