What was the first transaction which resulted in the very first bitcoin being mined OK, so I understand that bitcoin in introduced into the system when mining is performed. And mining is a process of adding transactions records to the bitcoin chain of blocks. And transaction (mentioned above) is nothing but bitcoin transactions taking place, which needs to be securely computed and added to the chain of blocks.

Now, my question is when the first bitcoin was rewarded to the first miner (may be the second one, after Satoshi added the main block), what transactions were taking place which needed to be computed and added. Theoretically, there was a point when there were no bitcoins in the network, then how did it start.
It startet with the rewards of the first blocks. After the genesis-block, there were 50 bitcoins in total, after the second block, there were 100 bitcoins in total, 150 after the thrid block...

This is the first block and the only transaction is a coinbase transaction (reward to an address). https://blockchain.info/block/00000000839a8e6886ab5951d76f411475428afc90947ee320161bbf18eb6048

And the following blocks do all look like that (only the coinbase transaction in all those blocks) until Satoshi made the first transaction from one address to another address (in block #170)