It depends on what you want to do at the end, if you don't care about having a perfect geometry and you want a quick fix in order to have a correct appearance, use the *Auto Smooth* option in the *Properties panel > Object Data > Normals*. It will smooth all the angles below the angle you'll set and keep the other ones sharp, therefore it will remove all these artefacts:

[![enter image description here][1]][1]


  [1]: https://i.sstatic.net/UXw7q.jpg