How much equity can we buy from open market

say i have to invest in a small cap company .can i buy shares worth 5-6 crore from normal market window as i see in market depth not that much sell orders are there to execute buying order of few crores

Possible, you may not get this on a single day, but maybe over few trading sessions, you can.

Got it.please share if you have past experiences like impact costs btw thanx for answer