Which shares i should buy keeping 10 years and 20 years holding time ?

 It is good that you have thought of holding shares for 10 years and 20 years duration , however, it is difficult to suggest any stocks with that kind of time frame in mind. All companies go through ups and downs in their journeys, and this could be reflected in the intrinsic stock price movements over a long period of time.

However it would be a good idea to identify some good large cap companies, which have a consistent ( more than 5 year ) track record of increasing sales and profitability as well as growth in market share in various industries. Thereafter one should enter with a long term view in mind. However, it is imperative to keep reviewing the company performance at least once a year so as to validate the decision taken in having invested in the company. Over a long time horizon of 10 / 20 years, having invested in good performing companies would tend to create wealth.