Grafted cacti

[gardener21900]

Hello everyone, I just bought my first grafted cactus yet I don't know how to take care of it. I did some research and found that the cactus on the top is a peanut cactus (thats all I know). its pretty big and looks healthy but I want to make sure it does not die. The weather in my country is perfect for growing cacti and I have grown at least 25 helthy cacti. if anyone can help with my situation I would appreciate it .