Beginner Gardening: please help me help my cactus!, 1 by mrs_heisenberg

mrs_heisenberg wrote:
hello! i have a leaning tower of cactus and it needs help! i don't know what kind of cactus it is but i got it from a friend from somewhere in south america. i planted it in the ground in florida. it's been growing for about a year now and as you can see, it is listing badly. seems to also have some black areas and white areas on it. i'd like to know what i should do to help this guy get heathy again. any ideas or suggestions would be welcomed and greatly appreciated!!
thanks!