E Invoice need to each & every bill or only 50 of the tax invoice

yes you are right that e-Invoice is for B2B not for B2C.

Also there no no such condition that only 50% you have to Generate e invoice for all B2B Transaction including Debit and Credit Note. 

As per the valuation rules and time of supply provisions, Invoices has to be generated. else has to face Interest and penal provisions.

You have to raise E-invoice against all your B2B invoices. For B2C you can raise other than E-invoice.