Hi prajwal6898,
unfortunately, the simple answer to both is that you can’t.
HOWEVER:
The great advantage of CSVs is that it is a very simple text-based format. The disadvantage is that it is plain text only – so you cannot easily have styled text or formatting. However, if your “question explanation” does not contain any formatting (such as bold text, links, images etc), then the CSV Import tool has a hidden field.
The 14th column is where you can add your extra text. Just make sure to encapsulate it with double quotes "
As for the UI scale, looking at your screenshot (thanks again!), it looks like you either A) have a small screen, B) are using a lower resolution, or C) have some kind of scaling activated (fractional scaling, or zoomed in with the browser). There is no real way to reduce this for you just for HD Quiz, but you can always use your browsers zoom function to “zoom out” of the page which will make things smaller.
For most browsers you can hold CRTL on the keyboard and then use your mouse wheel to zoom in and out. CTRL + 0 will reset the zoom level back to default. You may need to dig around the settings/toolbar of your browser if this does not work for you.