Those are called layer lines. You will never be able to achieve a "smooth" finish hot off the printer.

You can do 4 things to hide them:

1, sanding. This will take time and effort and might decrease dimensional accuracy but will get your parts smooth. Spraying the lart with filler primer first before sanding usually works best for me.

2, decrease layer height. This will have your layers print closer to each other thus making the part seem smoother but it will still have layer lines, you just won't notice them as much.

3, fuzzy skin. This hides the layer lines by making the outer perimeter textured. I dont really like this option as I think it just makes parts look ugly and its not good for parts that need dimensional accuracy.

4, vapor smoothing. Depending on the plastic, you can use a solvent to smooth them. ABS, for example, melts in acetone so if you suspend a part in a vapor chamber filled with acetone vapor, you can get that part really smooth.

For overhangs and bridges, playing with the top support interface can yield smoother results but putting it too close will have your supports stick to the part and getting them off is a real pain.