How is it right to be foolish or foolish?
SDURU is the adverb of a mode of action, answers the question how? how? It is always written together, it is used mainly in the colloquial style of speech:
He foolishly went in the wrong direction and disgraced himself.
S duru is not used in speech, since the ending of the accusative case cannot be combined with a preposition requiring the genitive case:
Well, what do you get from a fool?
The word foolishly is an adverb, answers the question how? and is written in one piece, for example, here is the following sentence:
Foolishly made a reservation.
There is also as a noun here is an example on this sentence
Do not take an example from a fool (from whom?)
The word "foolishly " is an adverb, answers the question (how?) and is written, unambiguously, together.
In the Russian language there is the word "fool", but when declining this noun with the preposition "s", we get - from a fool, from a fool, but "from a fool" - there is no such word.
We write correctly - foolishly, as well as - from behind, outside, early ...
He foolishly mixed up his shoes and went outside in summer boots.
Foolishly this one word is an adverb.
And with Duru, it's falling off something.
You can check by inserting any word between.
For example, in the bathroom to fall from the soap Duru. Slip.
I believe that the adverb Foolish is most often used in sentences and our speech, which is written in one piece, and which means Foolishly. In this sense, this word answers the question How? and it cannot be broken with a defining word.
But you can also imagine a case when this combination can be written separately, as a preposition with a noun in the form of the accusative case: He was the size of this fool (So what? - With a fool)