Hi @SrChong,
Welcome to the community 
I suggest looking through: Solidity learning resources
A good place to start with Upgradeable contracts is Learn guides: Upgrading smart contracts.
Then OpenZeppelin Upgrades: Step by Step Tutorial for Truffle or OpenZeppelin Upgrades: Step by Step Tutorial for Hardhat.
I also recommend reading: The State of Smart Contract Upgrades
For gaming I suggest looking at: