What is the ruling on working as a civil engineer in the construction of a headquarters for a bank that deals with usury, and is it obligatory to leave this work immediately, or is it permissible to remain in it temporarily to search for another job?

One should examine the fundamental operations of the bank. If most of its operations are unlawful (haram), then it is not permissible to work there. This applies to interest-based (riba-based) banks, even those that open an "Islamic window." As for Islamic banks that may conduct some transactions with a degree of doubt (shubha), but the majority of their activities adhere to Islamic law, then there is no harm in working for them. Similarly, the Islamic branches of riba-based banks generally fall under the ruling of Islamic banks. If the bank itself is unlawful, then it is not permissible to work in its construction, unless a person cannot find any permissible work through which they can earn their livelihood and the livelihood of those they are obliged to support. In such a case, they may work there while continuing to search for permissible work.