I am Rajat 20 yr old, student of Btech.
I am involve in masturbation from when I was 13yr old.
I want to know that is it harmful for me or my sex life?
Would masturbation affect on time during sex..
Will it affect my married life?
How shilajeet is useful?
What the work it does?

I don't know. It might not. But if its causing issues with you mentally you might want to speak with a sex thearpists or psycolgist or both or someone who speciliazes in both.

Unless you go blind from it or get hairy palms (thats a joke based on the old wives tales of what it can do))... in moderation its not going to hurt you at all.

AS far as the second part... I have no idea what shilajeet is as I don't speak that language.

I don't know of a 13 year old boy who does not. And most adult males do at least some. The issues it can cuase is all up to you. If you do it a few times a week, most likely none, if you do it 4 or 5 times a day, we may be having an issue.

So what issues is it causing you now ?