At Tanya Leighton, Berlin, the artist’s labour-intensive portraits suggest an art historical fever dream
At Braunsfelder, Cologne, a series of painted rubber plants speaks to our need for calmness
From a couture dress to a Soviet mural, the artist asks what counts as 'good' art
A survey at Kestnergesellschaft, Hannover, shows an artist in constant dialogue with the world
