Mining is probabilistic in nature: if you find a block earlier than you statistically should on average you are lucky if it takes longer, you are unlucky. In a perfect World pool would find a block on 100% luck value. Less then 100% means the pool was lucky. More then 100% means the pool was unlucky.
It depends on amount of active miners. The more miners work on pool → the more hashrate pool has → the more blocks are found by the pool. However the more miners are active → the less reward you get from each block found.
The estimated payout is a calculated using your percentage of valid shares on the total for current round. This percentage is then applied to the reward of the last block found by the network.
Since you start to mine your hashrate grows gradually. Please wait. The pool determines your hashrate based on the amount of shares sent by your mining rigs (workers). This value could be a little bit different from reported hasrate (in your mining software).
