1. ~ "It was a blunder mistake."

Correction, people! The word 'blunder' means mistake, so you could say:

~ "It was a blunder," or
~ "It was a big mistake."

 2. ~ "It would have been more better."

The word 'better' itself implies that the option in question is superior -- the use of the word 'more' in the sentence is, therefore both inappropriate and unnecessary. Thus the correct sentence would go as follows:

 ~ "It would have been better."

 3. ~ "Why don't he get married?"

The term 'don't' applies when discussing a plural subject. For instance, "Why don't they get married?" The right way to phrase that sentence would be:

 ~ "Why doesn't he get married?"

 4. ~ "I want two Xeroxes of this card."

The term 'Xerox' is used in North American English as a verb. Actually, 'Xerox' is the name of a company that supplies photocopiers! The correct thing to say, therefore, would be:

 ~ "I want two photocopies of this card."

 5. ~ "Your hairs are looking silky today."

This is one of the most common Indian bloopers! The plural of 'hair' is 'hair'! Thus:

 ~ "Your hair is looking silky today."