Q: finder freeze

Since one of 2 weeks Finder does not work properly.

I start up my iMac and when it is completly run the startup procedure, I click on the finder button in the dock.

Finder will open a window but will instantly freeze or after one or 2 clicks on a folder of subfolder it freezes.

Nothing will react after that, I cannot close the finderwindow with the red cross in the upper left corner. The only solution so far is to go to the Apple and select 'Force stop' and force Finder to stop, close the window and restart.

This in not convenient. It blocks my normal usage of finder and it is not possible to normally browse my files, copy, replace, ...

Does anyone has an idea what is wrong with my iMac? I have 10.9.6 installed.

Thank you