Complex sentence: Müller attended the peoples'school in Krefeld from 1922 until 1927 and then the middle school in Essen (Altstadt), he graduated in 1933, and started as an apprentice with an architect's firm in Essen.
Split into simpler sentences: Müller attended the peoples'school in Krefeld from 1922 until 1927 and then the middle school in Essen (Altstadt). He graduated in 1933, and started as an apprentice with an architect's firm in Essen.