Complex sentence: After returning to Germany (he joined BMW in 1984 as a senior designer), he was invited by the president of R&D of Porsche AG to join the design team (Porsche Styling) under the lead of Harm Lagaay (also from BMW).
Split into simpler sentences: After returning to Germany he joined BMW in 1984 as a senior designer. He was invited by the president of R&D of Porsche AG to join the design team (Porsche Styling) under the lead of Harm Lagaay (also from BMW).