Go to Edge Geometry Mode and select the left edge. Hold down Shift and drag the edge several times in order to cover the basic curvature of the tooth brush. Scale, move and rotate the edges to cover the dark blue region of the toothbrush. If needed, go into Vertex Subobject mode as well and adjust your geometry.
Now work with both Front and Top viewports to arrange the vertices in the Top Viewport as well. Select the vertices in the Front Viewport and move them accordingly in the Top Viewport. For the "S" area of the toothbrush body it is better to select the vertices and rotate/move them as a group to keep your geometry clean.
After you're done arranging, switch to Border Geometry Mode (shortcut: "3") and click any outer edge of our geometry. This will select the border of our object (formed by all "outer" edges). In the Top View, Shift+Drag to give some depth to our toothbrush. With the border still selected, in the Edit Geometry rollout, click the Z square near Make Planar. Now drag the border further more towards the middle of the toothbrush.
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