Thank you! :)
Hahaha every cactus grower is a cactus killer :D
I have killed so many I don't even want to count.
The safest is always dappled sun. They don't usually enjoy full sun all day long (well.. most anyway). Or some morning sun and then bright shade.
Everyone has different conditions and with time you will learn what is good for them. What for me is light shade, for you might be too dark. When they don't get enough light/sun they will grow deformed, they will stretch in search for the light.
If the sun is too strong, they will get sunburn - easy as that :) Some cacti are tougher than others too and will like more sunny spot. Or at least will not complain as much.
That's why it is good to know the name and check online what their natural conditions are. It is always helpful.