Reducing Ethereum gas costs for crypto exchanges using layer 2 platforms.

[AlirezaEthDev]

As I researched on reducing Ethereum gas costs for crypto exchanges using layer 2 platforms, the use of these platforms is beneficial for an crypto exchange when the users of that exchange, after bridging their ethers to layer 2, execute transactions that their "from" and "to" must be in layer 2, otherwise, if "from" or "to" is in the Ethereum mainnet, then that transaction must be sent from Ethereum to layer 2 or from layer 2 to Ethereum, and in this case, the Ethereum gas fee must be paid. Is my conclusion correct? If yes, is there a better way to reduce gas costs for transactions that their "from" or "to" are in Ethereum mainnet? In general, what is the best solution for reducing Ethereum gas costs on an crypto exchange with low user scale?