Automate

Anonymous 

It depends... You old data will disappear if you overwrite your "old" old data in the excel Sheet/Table with new data. If you just add data to your old (adding new rows in the excel sheet/table), you old data remains intact (in the sense that it still exists in your data model; whether your visuals will change depends on what measures you are using)

Here are some links you can read/watch:

https://docs.microsoft.com/en-us/power-bi/desktop-import-excel-workbooks 

https://www.youtube.com/watch?time_continue=34&v=hIbqjqp-hdc&feature=emb_logo

https://www.youtube.com/watch?time_continue=1&v=l_CgIOwSjmU&feature=emb_logo