Profile card using CSS with rem dimensions

I'm a newbie and picked this as my first challenge. I tried out doing this using rem rather than pixels. All feedback is appreciated.

I also have some specific questions:

1. I tried using CSS grid to center the card both horizontally and vertically. It only centered horizontally so I needed to add in a top margin. What's the best way of achieving vertical centering?

2. I used negative margins to position the larger blue circles as background images. Is there a better way of doing this?

3. There is a blue inner border on the image of Victor, as well as the white solid border I specified. Why is this and how can I remove it?