Original: As such, following the death of Friedrich Ebert in February, 1925 he temporarily acted as head of state of the Weimar Republic from 12 March 1925 until 12 May 1925 when the next president, Paul von Hindenburg, assumed office.
Simplified: After the death of Friedrich Ebert in February, 1925 he was acting president of the Weimar Republic from 12 March, 1925 until 12 May, 1925 when the next president, Paul von Hindenburg, was elected and assumed office.