What is the ruling on borrowing from "HSBC Qatar" Bank—which offers Islamic financing through Tawarruq and Murabahah, and buys and sells copper to the client in installments—for the purpose of investment and partially for marriage?

True Tawarruq (monetization) is permissible for any permissible intent. However, if the bank sells equipment to the client and then, by custom or explicit agreement, undertakes to sell it again on behalf of the client, this constitutes organized Tawarruq, which resembles the prohibited Bay' al-Inah (buy-back sale).