trouble with normal

after doing a boolean operation, and fixing all the edge so as to get a better flow of poly, i can t get ride of normal troubles. all are pointing outward there is no face inside the mesh. but normal are not perpendicular to face.some are going slightlu on left or right…
And when i set it smooth its really ugly.
by the way how to do some smothing group?
and for all those who already help me and the ones that will. thanks
I usually working on maya but i decided to learn blender for my next project so as to get 100% free software.

because all object like tube or cylinder got weird normal at creation. and there is no tool to correct normal. but to expalin what i do :
i create a tube, supress some faces to make hole, select all remaining faces then extrude.
and all the normal are wrong.

If normals are incorrect, try ctrl-n to recalculate them to point outwards. If they are still wrong, you can press the ‘Flip Normals’ button in the mesh tools panel (f9), to manually flip a faces normal.

If neither of those work, perhaps show a screenshot/picture/blend to see if it can better be helped.

I’m not sure 100% what smoothing groups are, but you can selectively apply set smooth to faces just by selecting the face and pressing set smooth.

If you are looking for subdivision (which is applied to a whole object), its under modifiers.

as you can see the normal are not perpendicular to the surface.
maybe it come from my process.

Normals sometimes get messed up when you scale or move vertices in edit mode. Try doing a Ctrl-A in object mode to Apply Scale and Rotation, sometimes that fixes this.

CD38 has a point but somehow your whole object looks…awkward. There are several sides with three or more normals (look on the rightmost faces, for example) which isn’t normal either, these faces seem to be rotated or something. It’s hard to judge but maybe you need to clean up your model a little more as well.
Also, another thing - try to stay away from booleans in Blender. I’m generally not a fan of them when doing Polymodeling - maybe they are just so much better in other applications but for now, in Blender, you might have to accept that their results are just bad, when it comes down to mesh topology.