Select and nominate 1 to 16 trusted validators (staking providers). If more than 128 nominators nominate the same validator, it will be "oversubscribed" and only the top 128 nominators with the highest staking amount will be rewarded. In other words, if a validator is oversubscribed and the staking ranking (in order of increasing staking volume) is 129 or higher, it will not receive any staking rewards.
Please note that you will need to claim your rewards manually using the functions in the Staking tab. Staking rewards must be claimed within 84 days after they are generated. If you do not claim your staking rewards within 84 days, you will not be able to claim them and you will lose a portion of your staking rewards. However, you don't necessarily have to claim your staking rewards within 84 days, because once someone who has access to the staking pool clicks on the claim button, the rewards will be credited to all users who have access to the same staking pool.
You need to unstake a staked token before you can send it. However, the token will be in the "request to deactivate" status for 28 days after deactivation, and you cannot send money immediately. This period when you cannot send money is called the "lock period". After the 28-day lock period, you can withdraw your DOT using the "Withdraw" function. Please note that you will not be able to get any staking rewards during the lock period.