You should actually update your service description and ToS to mention the fact you don't represent your own liquidity and instead resell a third-party exchange Gate.io and rely on their AML/KYC policies to avoid misleading people.
Not only that, but the exchange fees are more expensive than Gate.io. exchanging 1 Bitcoin is equal to 18.39840927 Ethereum, while in Gate.io you get 18.66. It may pose a problem as Gate.io prevents any transfers without completing identity verification, so if the service depends on the Gate.io API, it may be blocked.