can i update the product stock using upload the csv file ?
Indeed. You can do so with our ATUM Export & Import PRO add-on.
Also i Want to update stock automatically so which add on i will purchase for this requirement can you please help me for this ?
Actually, our export add-on supports automatic and scheduled exports but not automatic imports. So you should do this process manually.
Automatic imports is a planned feature that will come on a future version though.