Complex sentence: Nikolaus started to fortify the crumbling castle and refurbished it with the services of Vienna builder Simon Retacco from 1630 to 1634 and with Domenico Carlone from 1643.
Split into simpler sentences: Nikolaus started to fortify the crumbling castle. He refurbished the castle with the services of Vienna builder Simon Retacco from 1630 to 1634 and with Domenico Carlone from 1643.