For something like that I would use Curviloft on the bottom, too. There are some places where you are likely to have problems because the upper surface drops below the rim. Is that the way you want it to be? Also make sure you correct the face orientation so white front faces are out. What version of SketchUp are you actually using? Your profile says "2019 Make/Free" which doesn't exist but the file you posted is V2017. Knowing the real version will help us help you with the sorts of tools you can use.