Widget font size, style

You can change font-size by style-sheet.

I found simple way and paste below code in Additional CSS

.tribe-list-widget .tribe-event-title {
    font-size: 14px;
}

but how to decrease space between the lines of tribe-event-title and tribe-event-duration (events listed in Events Widget) ?

how to control the space, to have something like this: https://imgur.com/a/Hu87h

try line-height see if it works line-height: 70% or 80% and it should bring them closer together by removing the space.