Problem with STL File

I was trying to make some revisions to an STL but the file has some problems.. I think it is the base because it has many random polygons instead of being smooth.  I loaded it into TinkerCad but I keep getting errors if I try to 'combine' it with anything else.  I also tried to fix it with Netfabb first but that didn't help either, although I just used the auto repair.  I tried bringing it into DesignSpark too but it imported as a mesh which I couldn't edit.

Can someone here find a way to smooth out the base or have an idea how I can fix it?  

Here is the STL:

Try this

Sorry gave you a crappy version at first 

Thanks Tech! :)

 I am able to work with that one.  The bottom sides are not as smooth but I can edit that now at least.

No problemo

I noticed that as well but when I loaded it in Zsuite and did a print preview it looked like it wasn’t noticeable so I just kept it the way it was.