Powerapps, Powerbi and Sharepoint

Please find the scope of the project below.

1) We need to have a power app that gets data from the user. (Simple data like numbers, text)

2) In step 1, there are certain fields that fetch data from excel spreadsheets. These spreadsheets are stored in my onedrive. Totally, 3 source files are present.

3) In addition to fetching data in step 1, there is also some manual entry for certain fields.

4) Once we have everything, this entire data should be stored somewhere (please suggest)

5) All stored data in the form of excel to be exported as table in Power BI and some manual calculations (Addition & multiplication) done and final data is now ready.

6) Pick only certain columns from step 5 and finally upload them to sharepoint. In addition to the two columns selected in step 5, there are few other fields for which users need to enter values and finally submit to sharepoint. I am thinking of this step 6 done via powerapp.

Please propose the best possible solution as I expect the completion of the project ASAP.