following few lines are inappropraite usage of certain highlighted(in the brackets) words.Can someone plz tell me the defect in the sentences.

1.Ranjit may [help] himself with the beer in the fridge.

2. How do you deal with a friend who doesn't listen to a [reason].

3.Your suggestion look great on the [paper],but are absolutely impractical.

4. My wife runs profitable [business] in this suburb.

5. Customers have to [service] themselves at this canteen

please help me out in detail with the modification of the above sentences.
Hello, English exhilaration Emotion: smile

This is how I'de rewrite your sentences, but I don't see anything wrong with most of the verbs in square brackets. The "mistakes" seem to be somewhere else in the sentences.

1. Ranjit may help himself to the beer in the fridge.
"To" instead of "with". "To help (oneself) to" means "to take something for oneself".

2. How do you deal with a friend who doesn't listen to reason?
I deleted the article "a". To "listen to reason" is an expression that means "listen to sensible advice".

3.Your suggestions look great on paper, but are absolutely impractical.
I deleted the article "the"; "on paper" means "in theory", "written down or printed, but not tested by experience".
Also, "suggestion" needed an "s" for the plural.

4. My wife runs a profitable business in this suburb.
I added "a" before "profitable business". "Business" is used as a countable noun in this sentence.

5. Customers have to serve themselves at this canteen.
You "serve" food or drinks, not "service".

I hope it helps.

plz help me,somebody plz take a look on the sentences
 miriam's reply was promoted to an answer.