Is it permissible to take a loan from a brother with an agreement to repay it with a master's degree or to waive it in the event of not completing the study, in exchange for the borrower covering the lender's expenses for study and food while she accompanies him to study abroad?

The scholars have agreed that every loan that draws a benefit is usury (riba). So, if you borrow a sum of money from your brother on the condition that you spend on him from it, this is not permissible. As for your agreement that if you succeed and obtain the certificate, you will repay him the amount, otherwise, he will forgive you, this is considered a suspended gift.