No problem,
A couple of questions, what is your Engine Scalability Settings set to? To check this go to your settings in your active viewport and click on the dropdown box. Go to your “Engine Scalability Settings” and make sure they are on High and Epic settings to get a high quality image.
Also go into your project settings under Edit. Find the rendering section under Engine and under default Postprocessing Settings make sure you are using Temporal AA under the Anti-Aliasing Method.
Also a good way I like to take screenshots, I use the snipping tool which allows you to actively crop the area in which you would like to capture. The snipping tool is a device under accessories in your Windows Start menu. I hope one of these solves the issue you are having.