Short answers, pulled from the story.
Gustav Mahler was born on the 7th of July 1860 in the village of Kalischt (Kaliste) in Bohemia, then part of the Austrian Empire. His family moved to the city of Jihlava (Iglau) in December 1860, where he grew up.
Mahler converted to Catholicism in February 1897 to overcome the bar that existed against appointing a Jewish person to the directorship of the Vienna Court Opera (Hofoper). Despite this, he has been described as a lifelong agnostic.
Mahler met Alma Schindler in November 1901 at a social gathering and they married on the 9th of March 1902. Their marriage was marked by tension over Mahler's insistence that Alma give up her own composing career. After discovering in 1910 that Alma had begun an affair with the architect Walter Gropius, Mahler sought advice from Sigmund Freud and subsequently encouraged Alma to resume her music.
Mahler's music was banned as degenerate during the Nazi era, which effectively prohibited its performance across much of Europe. During the German occupation of the Netherlands, performances of his works were restricted to Jewish orchestras playing for Jewish audiences alone.
Mahler completed nine numbered symphonies, plus Das Lied von der Erde, which he declined to number. He worked on a Tenth Symphony in the summer of 1910, completing the Adagio and drafting four more movements, but it remained unfinished at his death. None of his final three works, the Ninth, Das Lied von der Erde, and the incomplete Tenth, were performed in his lifetime.
Mahler was diagnosed with bacterial endocarditis, a disease to which people with defective heart valves were particularly prone. He conducted his last concert at Carnegie Hall on the 21st of February 1911 with a temperature of 40 degrees Celsius. He was transferred to the Löw sanatorium in Vienna in May 1911, where he developed pneumonia and died on the 18th of May, aged 50.