How can one invest saved money in a halal way to preserve capital and spend from the profit, given the absence of a trustworthy person for investment, the investor's lack of understanding in trade, the Islamic banks' failure to yield sufficient returns for zakat, and the need to avoid dealing with usury in conventional banks?

Investing and growing money is a good thing, but it is not permissible to deposit money in usurious banks, because their usury is forbidden by Islamic law. A Muslim must seek what is lawful, even if it is little, for lawful earnings bring blessings, a happy life, and answered prayers, while unlawful earnings wipe out blessings and cause a constricted life. Money can be invested by entrusting it to a trustworthy person who can trade with it for a percentage of the profit, or by investing it in Islamic banks, or by searching for a permissible project that suits your academic situation with the help of experts.