What is the ruling on zakat for money that has been partially spent and property that has been partially sold, and how is zakat calculated for stocks that have decreased in value, and is it permissible to give zakat money to a poor brother to help him get married?

Zakat (definition) is obligatory on cash and trade goods if a year has passed on them and they have reached the Nisab (definition). The Zakat for each year must be paid immediately based on the amount available at the end of the year, and a decrease in wealth does not nullify the Zakat. It is permissible to give Zakat to a relative if they are among those eligible, and the reward for that is greater.