Yes it’s a basic question, but searching this forum hasn’t gotten me very far.
Since SketchUp has no pen/bezier tool, I’m not sure of the easiest way to draw geometrically perfect curved lines like the ones in the attached image (which I draw in illustrator). The freehand tool won’t do it and I’m not clear on how the arc tool can help with inside curves. Plus, it doesn’t work at all with small curves (too many segments error, which is a whole other pain in the butt).
What version of SketchUp are you using? That will determine what tools are available to you.
You can probably do what you want with the native Arc tool. Or maybe an extension would be appropriate if the version you are using can use them.
What is it you are modeling. Might be that you only need to work at a larger size. How will the model be used once you’ve created it? Will it just be a flat thing as in your image.
Just eyeballing from your image. Nothing but the Line and 2-Point Arc tools.