hey,
I wonder, even if the probability so small is, if someone else get the same private key as me could he/she spend my Bitcoins and viceversa? would we have the same Bitcoin Adress?
you may not necesarily have the same bitcoin account as it changes upon every transaction depending on the wallet you are having its keys (not exchanger wallet). but be rest assured that it is one private key to one wallet. whether or not the private key is in the hands of two people but also note that the algorithmn can not generate two identical private keys on its blockchain as it was not design to perform in that capacity.
Which algorithm are you talking about? Addresses are not generated on blockchain. There is no algorithm that checks if a private key is already into use. There is no record of any private key on blockchain.
Also, one private key doesn't mean one wallet. One private key means one bitcoin address. The example you gave in which Bitcoin Address change after each transaction is HD wallet which is generated using seed which is derived from mnemonic code and passphrase. I don't know why I am explaining at all, your bitcoin knowledge is horrendously wrong.