Complex sentence: After submitting a habilitation dissertation, for almost two years he left for the United States, where he worked from 1973 to 1975 as Research Associate Professor at the Vanderbilt University.
Split into simpler sentences: After submitting a habilitation dissertation, he left to the United States for almost two years. There, he worked from 1973 to 1975 as Research Associate Professor at the Vanderbilt University.