Supply bottlenecks with timber, steel and insulating material are causing construction stoppages in Germany and threatening to slow the country's recovery from the coronavirus slump, building associations said on Friday.  The German economy, Europe's largest, shrank more than expected in the first quarter due to COVID-19 restrictions, but upbeat business sentiment surveys are now heralding a swift summer recovery.  The strength of the rebound depends on how much consumers will splash out once curbs are lifted and how much manufacturers will be able to overcome supply bottlenecks.  Roofers, who ...