how many of my shares is one share in the pool?
1 share from the miner = 256 shares in the pool, but the important factor is your overall difficulty, not shares.
I find the shares and the pool shows zero
I don't know what your math but it seems that for some blocks no payout
Look in "Statistics-> Round Transactions" and find your username there.
Yes, "Shares" is 0 for some rounds, but you still have reward because difficulty is calculated, not the shares, thats what I've tried to explain you.