You need $5 worth of CBY per each tree staked to be able to stake (i.e. 50 trees = 250$ worth of CBY)
If you decide to unstake the NFTrees, the $CBY will be returned minus a fee. In the first year, the fee is 7.5%, it reduces to 3.75% in the second year, and after that, the fee drops to 1.75%