Need Help,Text File Upload,Open,Read,Rewrite and Save Download

I have a lot of files that want to replace some new words instead of the old ones.
Because I am not familiar with the file operation. I hope someone can help me.

1 Use the control module to upload and save files to a specific folder.

2 Open the file in multiple lines Text box, for processing use. (I have done the processing part already)

3 After processing save the new text to the new file.

4 Download the file. I can do it through the link.

Thank you for your help. I would like to pay for you.

Please contact me and give me your rate. Thanks.