Quantitative Easing, How does it work?

Quantitative easing is the process of increasing a money supply by the Central Bank or Federal Reserve. This money is used to buy a government securities or other securities from the market. So how does it work? ,
The point of this process is to make the bank decided to lend a money to people who are in needed of cash, (maybe a businesses). The banks didn't want to take a risk by lending their money to people who needed the money because anything could happens and they might not get their money back. So what the bank does is they take the money from the Central Bank, and instead of lending to businesses, they buy treasury. Now the Federal Reserve saw that there are people who needed money but could not get any because the bank won't give them the loans, So what the Federal Reserve does is to produce money and push it into the economy. This is how it's done, The Federal Reserve use the money to buy an assets or the securities from the bank, in other word, they take the pressure off the bank.
Then what happen next is the Federal Reserve will buy a treasuries, because the more demand that Federal Reserve created for the treasuries, The lower the yield(returns) becomes,  and if the yields goes down, it's mean the less incentive for the bank to buy those bonds as it will not make any profits from it.
So when this happen, it actually forcing the bank to find a way out, anything that will make them a profit. This forces the bank to finally lend the money in their bank to those people or businesses that needed the money at the first place, This process make the bank stop buying treasuries to lending a regular loans to the wide market. And in case if the QE still not working, the Federal Reserve will put money in to the system, which will devalued the Dollars

Further Question

How or What will make the QE not working/ failed?


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