Short answers, pulled from the story.
Abel Seyler, a Hamburg merchant and banker originally from Switzerland, founded the Seyler Theatre Company in 1769. He had previously been the main owner of the Hamburgische Entreprise, whose dramaturge was Gotthold Ephraim Lessing.
The play Sturm und Drang, written by Friedrich Maximilian Klinger for the Seyler Company and first performed in 1777, gave its name to the entire Sturm und Drang literary and artistic movement. Klinger was employed as the company's house playwright at the time.
In 1789, Friederike Sophie Seyler published a Singspiel called Hüon und Amande, which was plagiarized by the troupe of Emanuel Schikaneder and greatly influenced The Magic Flute. Friederike Sophie Seyler was Abel Seyler's wife and a celebrated actress.
Between 1777 and 1778 the Seyler Company employed some 230 actors, singers, and musicians. When it was founded in 1769 it comprised around 60 members, including an orchestra, a ballet troupe, house dramatists, and set designers.
The Seyler Company performed at the Weimar Schlosstheater for three years, invited by Duchess Anna Amalia of Brunswick-Wolfenbüttel. Contemporaries described Anna Amalia's securing of the company as "an extremely fortunate coup."
Works composed for the Seyler Company include Ariadne auf Naxos and Medea by Georg Anton Benda, and the opera Alceste with music by Anton Schweitzer and a libretto by Christoph Martin Wieland. The company played a significant role in the development of serious German opera in the late 18th century.