So let's put it all together:
Side scroller definately. You play a guy, maybe.
Keyboard controlled, maybe
You start off in a forrest maybe.
In some parts you walk on clouds.
Something about a bridge or a well being guaded by a monster or something.
You maybe could collect items.
Maybe collect fruit.
Some bits had a castle in maybe.
VGA graphics.
from the 90s, it came on a floppy disc.
Legend of Kyrandia is the closest so far.
So, here's my guesses. Was it an actual side scroller or a 3rd person advernture like
Kyrandia? For the visual style like Kyrnadia but in a side scroller there's
flashback or
Prince of Persia or
Another World. Anything in the neighborhood?
For content, (although I don't remember a monster on a bridge, but know knows) is the
Captan Comic series close?
That's all I've got for now.