Removing 50Hz flicker on lights
No doubt of it, that's a fluorescent.  Lights like this give fluorescents a bad name.   Fluorescents are really quite good these days. 

Pop the cover off, get the model number and figure out what type of bulb it takes.  See if you can lay eyes on the ballast itself, to get a sense of its shape and size.  

From there, go shopping for an electronic ballast for that bulb type.  Look for one that will physically fit in that fixture.  The shape and mounting are highly standardized.  An electronic ballast will not flicker or buzz, will start instantly (or quickly if it's a rapid-start or programmed start) in all conditions including deep cold.