Speedy nodes are not working

is this function only available at moralis ?

Moralis uses ethers.js. If you want to use web3.js, you will need to include it separately.

(await this.web3Js.eth.getAccounts())[0];

Where did you get this code from? It should be web3.eth.getAccounts() e.g. web3.eth.getAccounts().then(console.log);

You have to assign the Alchemy node as a HttpProvider first before you call Web3(), something like this:

const nodeProvider = new Web3.providers.HttpProvider(<YOUR ALCHEMY NODE>);
const web3 = new Web3(nodeProvider);

You can then start calling web3jsā€™ web3.eth.getAccounts([callback]), you can refer to web3jsā€™ documentation, you donā€™t necessarily have to use Moralisā€™ Web3 API for everything.