How to make transaction with NBitcoin?

I was working on sending bitcoin from one address to another. I followed this article: https://programmingblockchain.gitbook.io/programmingblockchain/bitcoin_transfer/spend_your_coin#sign-your-transaction . Every thing is fine as expected, i created a Test wallet, added amount in it and made my first transfer. Now i wanted to make my second transfer with the same code but there is one transaction Id that is made static:

var client = new QBitNinjaClient(network);
var transactionId = 
uint256.Parse("0acb6e97b228b838049ffbd528571c5e3edd003f0ca8ef61940166dc3081b78a");//Here the transaction Id is kept static
var transactionResponse = client.GetTransaction(transactionId).Result;

Now how can i perform second transfer if we keep the same previous transaction Id?

or is there a way where we can get previous transaction Id of an address?

Thanks!