i got a crassula like 3 days ago and i noticed today the stem is cracked and is also brown. I think it is because i keep the plant next to a window all day but where i live there is barely any intense sunlight
This is normal, as it will eventually develop a woody stem. Just to be on the safe side, though, I would recommend letting it dry out pretty well between waterings.
Here is an article for more information:https://www.gardeningknowhow.com/houseplants/jade-plant/jade-plant-care.htm