How can I dispose of the money I took from the travel allowances, the amount of which I do not know, so that my repentance to Allah may be complete?

Taking money from the school is Islamically forbidden because it is a breach of trust, and the Shari'ah texts condemn such acts and command fulfilling covenants and trusts. Whoever does this must repent to Allah Almighty, and the conditions for repentance are four: abandoning the act, feeling remorse, resolving not to return to it, and restoring the right to its owner. If one forgets the amount, they should return what they most likely believe will fulfill the right, and it can be returned through indirect means without the knowledge of the officials. If it is impossible to pay back the remaining amount, one must seek absolution from the school's owners.