I have a question about the expression "How much is right to do something?".
Is it correct at all? I mean, when someone proposes me to do something, but I have a doubt about that action I ask "How much is right to do it?". Or should we ask "How much is it right to do it?" or in any other way?
To explore the origin of that it, let's take an example sentence:
Playing practical jokes is acceptable.
In order to ascertain the extent to which it is acceptable to play practical jokes, you first remodel the sentence:
It is acceptable to play practical jokes. (It is a dummy pronoun)
Next, you reverse the subject "it" and the auxiliary verb "is": it is -> is it:
Is it acceptable to play practical jokes?
Next, you add an adverbial phrase, such as "to what extent":
To what extent is it acceptable to play practical jokes?
Or, simply move the adjective "acceptable" in this adverbial position and add "how":
How acceptable is it to play practical jokes?
It a similar vein, your sentence should have that it:
How proper is it to do something?
I changed "right" to "proper" and ditched "much" to comply with FumbleFinger's comments.
No, it is not correct, as @CopperKettle's answer explains.
However, in your situation:
someone proposes me to do something, but I have a doubt about that action
A more normal way to voice your doubt, asking if it's right to do what they propose, would be to just ask someone:
Is it right [to do that proposed thing]?
Or, to emphasize that
Is it really right [to do that proposed thing]?
You can replace "right" with synonyms like "ok", "proper", "acceptable", "correct", etc.
Unless I misunderstood your description of the situation, I think that final example would be the most idiomatic way to say it.
I wouldn't use that phrase at all, but instead say "How much should I do it?"
This flows much better.
