Nice start on the model. As @davidheim1 said, next, add the joinery.
I agree with Ian’s suggestions. You’ll find it is easier and prone to fewer errors.
As for your modeling, I think you’ll find it easier and faster if you get in the habit of drawing the parts in place where they’ll live. This allows you to use what you’ve already drawn as references, you don’t need to know as many dimensions up front (let SketchUp tell you the dimensions) and again, less chance for errors.
As an example from the axis alignment, it looks like you drew the back standing on end on the ground plane. If you did, then you would have needed to rotate the component several times to get it into place. Or did you change the axes while or after making the component?
In either case, with the axes oriented as they are, dragging another copy of the component into the model space would have it standing on end. Look at how it appears in the In Model components collection.
Another thing you can do to make your modeling easier is leverage the ability to copy and flip geometry to make symmetrical shapes. You can see that the curves aren’t the same left and right on the back piece. Instead of trying to draw mirrored curves, draw them on one half and copy them to the other side.
An easy way to do that is with the copy function of the Rotate tool.
I would suggest using precise dimensions. When your dimensions are only approximate as are most of yours, modifications to the model will be more difficult. And if you plan to build this for real, it will be difficult to intentionally create parts with those dimensions.
It’s also helpful to give the components useful names as you go. With a list of parts like this, it’s difficult to tell what is what.
Keep plugging away and it’ll all fall into place.