One of the “tricks” with modeling something like this is deciding where to start and what to do first, second, third, etc. I can easily think of three or four different approaches to modeling this sort of thing. In this case I started with the back as a long rectangle. I used the 2-Point Arc tool to put the radii on the top two corners and then use Push/Pull to give it thickness. New users often tend to draw a thing as if it’s entirely 2D and then try to make it 3D afterwards. This leads to problems with missing, reversed, and internal faces. I gave it the 2mm thickness before I outlined the recess just using Offset and then I pulled the outer region out to create the recessed area.
Next, I drew lines at the ends to separate the bottom front edge from the rest, used Push/Pull to pull the lower lip out and then moved the edge, shown selected) back to create the bevel on that lip. I could have pulled the face out by the shorter distance and then moved the bottom edge out a little more to create that bevel, too.
To create the bevel on the inside of the recess I drew a line defining the top of that bevel. Then I moved the line shown selected out. If you remember your high school geometry, to get a 45° bevel there, you move the line the same distance as the height up to the fold line.
Then I repeated the process on the back. You could also draw a triangle on the end and use Push/Pull to push away the waste.
Now before creating the bevel on the edge around the sides and top, I softened the edges so the lines between the curved surfaces and the flat ones aren’t visible. Then I made the thing a component and checked to see that it reports as solid in Entity Info. (It did since there are no holes or other issues.) Since you are using SketchUp 2019 and have access to the Solid Tools, I chose to make a “cutter” for the bevel. This involved using a profile (in green) and a path (the invert U-shape shown in blue.) I put in guidelines to show the alignment and the angle of the edge of the “cutter”.
After running Follow Me, I created a component of the cutter, making sure it was also solid. You could be using groups but for a number of different reasons I prefer components.
I moved the “cutter” into place against the light housing and then used Subtract to subtract the cutter from the housing to leave the bevel. I used Subtract from Eneroth Solid Tools because it respects components. The native Solid Tools will convert components they modify into groups. Not a big deal if you are using groups instead of components but if you have used components for a reason, Eneroth Solid Tools or Bool Tools 2 are better choices.
And after Subtract it’s finished business.
Edit to add: A couple of notes here. At no time did I do anything in the modeling process that resulted in holes or internal faces so I never had to worry about fixing those sorts of problems. There were never any exposed back faces once I had the shape 3D. Face orientation is important for 3D printing as that tells the slicer which side of the face gets the printing media and which side is air. I also erased coplanar edges as I went along.
Another option might be like this. Base and back, profile of the sides and top for Follow Me, then add in the inner and outer bevels.
