After studying Amitabha in Nanwu, I want to give it back to myself, my relatives and friends, and wish us health, safety and longevity. How can I return it?

Just say it. There is no fixed format for returns, but they are basically based on the principle of karma. In other words, when you return, you should know what you rely on, and rely on the good deeds that keep your heart steady. According to this good deed, you can repay them, and bless them. In Buddhism, the scope and order of return are generally teachers, parents, relatives and friends, and all sentient beings. The bigger the scope, the better.