how to account for application of donations ?

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- I receive various small donations to cover medical costs for a
certain treatment and I want to track how they are used against
Doctors Bills and other costs like transportation

- Payment for those Bills are made from the same bank account the
donations are received but also from other assets (like cash)

- In the end I want to see how what costs/Bills the donations have
been used for and whether there are funds left over

- also I have the situation that someone borrowed some money to pay
the first bill and should get a (partial) reimbursement once donations
have come in

Can anyone advise how to set this up? I do not have to report in
detail or each individual donation, but need to see the entire sum of
funds that have been donated and what bills they have been used for