Complex sentence: Wahid Khan, at a very young age, was first initiated into Dhrupad, Khayal and Thumri and then in trained extensively on the Sitar and Surbahar by his father Imdad Khan for many years.
Split into simpler sentences: Wahid Khan, at a very young age, was first initiated into Dhrupad, Khayal and Thumri. After which he was trained extensively on the Sitar and Surbahar by his father Imdad Khan for many years.