Frontend Mentor - Blogr landing page

I will very much appreciate it if you can give me some feedback about my case

1. In this challenge I use the grid to layout the page, and I use section to <section> to divide sections on this page, that I am confused about is on each section I use default padding to create distance between each section and the section height will increase to content, should I use min-height for each section? and when I should use absolute height.

2. are you have a reference to using margin and padding wisely?

3. I am still confused to set dimension to element, and when to use units in CSS like rem, px, and %, can you explain to me?

4. can you give me advice using positioning the element, like positioning the image on each section, I am still troubled and confused to adjust the element position.