Data from Sharepoint

ghouse_peer , as per my knowledge

1). When i have pulled data from sharepoint excel file and created report, next month the data gets updated and the updated excel file sould be pasted in the same location/ Should be replaced on that excel file in sharepoint.

Please check the link URL remains the same . So make sure the same file is overwritten

2) once either of the two is done from above point. When i refresh in power bi desktop will the reports get updated/refreshed accordingly?

yes

3) When i change my pc/ laptop what steps i have to take to maintain the same data connection and same reports in PBI desktop without affecting report and connections?

You may have to give credentials again in new PC

excel in SharePoint
https://community.powerbi.com/t5/Desktop/Import-Data-from-an-Excel-sheet-in-SharePoint/td-p/47223
https://www.youtube.com/watch?v=3GIz50pftZ0
https://www.youtube.com/watch?v=gJF2e_43FRY
https://whitepages.unlimitedviz.com/2018/07/excel-files-power-bi-desktop-sharepoint/
https://docs.microsoft.com/en-us/power-bi/connect-data/service-excel-workbook-files
https://powerbi.tips/2016/09/loading-excel-files-from-sharepoint/

https://www.poweredsolutions.co/2019/04/04/connecting-to-files-in-sharepoint-onedrive-with-power-bi-power-query/