Is the marriage contract considered religiously valid and enforceable, and is the girl considered a wife, given that the contract was written on a blank paper, in the presence of a foreign girl, and her brother objected to it because it was not officially documented?

The marriage contract is valid as long as it was concluded with an offer from the guardian's agent and acceptance from you, and in the presence of two witnesses. Its validity is not affected by not being written on a state-approved document, or by the presence of a foreign woman. Marriage in Islamic Sharia is a verbal contract concluded by uttering the offer and acceptance in a single session, in the presence of two adult, sane Muslim witnesses. The contract is valid and produces all its effects if it fulfills its legally stipulated pillars and conditions. As for documentation, it is a matter required by law to protect the contract from denial and repudiation.