Experiment with laying out simple elements on a single HTML file (where you can iterate more quickly), then when you have what you want, make those same changes in your React app
If you spend one hour on each of these, you may be surprised by how capable you’ve become. The rest, as others have said, you will pick up naturally as you work on your project.
Understand the box model
Understand flex box basics
Understand padding and margin
Experiment with laying out simple elements on a single HTML file (where you can iterate more quickly), then when you have what you want, make those same changes in your React app
If you spend one hour on each of these, you may be surprised by how capable you’ve become. The rest, as others have said, you will pick up naturally as you work on your project.