Hot to clean up model, created with boolean?

How do i clean up this to make it easy for further edits?
Can I join the flat faces into nGon?

Can I join the flat faces into nGon?
Blender doesn’t currently support ngons.
Select vertices and W / merge
Select 2 adjacent triangles and F to create a quad

Select everything and press Alt+J
Turns tris to quads

Also you may have some doubles. Remove those too

Removing doubles can also get rid of “close” verts too if you up the merge threshold (in the mesh tools panel (T)).

Another handy trick is individually merging excessive verts with alt-M or by edge sliding (ctrl-E) and then removing doubles.

might be faster to make 6 circles in the correct shape, and face together the edges to make that shape…
I was thinking about this. Could you please give more hints about the commands you would use to accomplish this?

Create a Circle with 32 Vertices, check “fill”.
Go into edit mode
Move the Circle up on the z-axis a bit more than 1 blender unit, say 1.05 or so.
Select all verts, duplicate and rotate around the y-axis 180 degree
Select again all verts and duplicate. rotate around the y-axis 90 degree
Duplicate the still selected 2 circles again and rotate 90 degree around the z-axis.
Now you should have the silouette of the desired object.
Remove in front view the left half of all verts.
Remove the lower half of all verts.
Got to side view and remove the front half all all verts.
Now add a mirror modifier and enable x, y, z and clipping
Go to edge select mode and connect 2 of the edges a time and press f.
There will be one triangle left in the middle, select all 3 edges and press f.
Finished, you may add an edge split modifier and a subsurface modifier to get a cleaner result if desired.

THNKS @cnikiel - his directions led to this.