Is a photograph showing a BMW car half submerged in floodwaters with a "F*ck you Greta!" sticker prominetly showing on the rear window real? No, that's not true: someone photoshopped the sticker onto a real image of a car flooded by water during heavy rainfall in Germany in 2021.
An example of the photo can be seen in this Facebook post that was published on July 18, 2021. This is what the post looked like on Facebook at the time of writing:
(Source: Facebook screenshot taken on Sun Jul 18 15:02:52 2021 UTC)
However the image was digitally manipulated. According to German newspaper Bild (archived here) the original image was taken by David Young in Beyenberg, a part of Wuppertal, during the flooding that hit the area in July 2021 after heavy rainfall and it does not show the sticker. The photo in question is the last one in the article.
A Twitter user by the name of @f_stiebeling pointed out a different picture of the same car at a slightly different angle that also didn't show the sticker (archived here):