How user can pay custom value of ETH with metamask?

Support Sending and Receiving Tokens
1

Hello!

  1. I want to give user possibility to choose his own value of Ether. How to do this?
  2. How efficiently change the network when pressing connect to metamask (for example when user will press this button metamask should change network to binance smart chain (ID 56)

here is my code.

										<!DOCTYPE html>
		<html>
		<head>
		<script src="https://cdn.jsdelivr.net/npm/web3@latest/dist/web3.min.js"></script>
		</head>
		<body>
		<div>
		<button class="enableEthereumButton btn">Enable Ethereum</button>
		<button class="sendEthButton btn">Send Eth</button>
		<div id="status"></div>
		</div>
		<script type="text/javascript">

		// Running on the page, in the browser
		if (typeof window.ethereum !== 'undefined') {
		  console.log('MetaMask is installed!');
		}	
		if (!ethereum || !ethereum.isMetaMask) {
		  throw new Error('Please install MetaMask.')
		}	
		/*********************************************************/
		/* Handle chain (network) and chainChanged, per EIP 1193 */
		/*********************************************************/

		// Do this:
		ethereum.on('chainChanged', (chainId) => {
		  /* handle the chainId */
		});
		const ethereumButton = document.querySelector('.enableEthereumButton');
		const sendEthButton = document.querySelector('.sendEthButton');

		let accounts = [];

		//Sending Ethereum to an address
		sendEthButton.addEventListener('click', () => {
		  ethereum
			.request({
			  method: 'eth_sendTransaction',
			  params: [
				{
				  from: accounts[0],
				  to: '0x6adress.................',
				  value: '0x00',
				  gasPrice: '0x0000001F6EA08600',
				  gas: '0x0001ADB0',
				},
			  ],
			})
			.then((txHash) => console.log(txHash))
			.catch((error) => console.error);
		});

		ethereumButton.addEventListener('click', () => {
		  getAccount();
		});

		async function getAccount() {
		  accounts = await ethereum.request({ method: 'eth_requestAccounts' });
		}
		</script>
		</body>
		</html>

Please help