Hi,
Unfortunately, I am unclear how you decided you had 3 columns for your example, will there be 10 columns other times?
So essentially, you have X number of rows, that you want to display. You want them to populate the blank rows (or maybe update them?????????) and then you want to submit them.
Also, it looks like you are asking how to do it, with multiple Rows at a time. In your example you have essentially 3 rows, because you have pivoted your data from the table to be vertical.
Do they have to be able to edit many at once? The standard way for this would be to have a Gallery that horizontally shows all your rows, (not hori/pivoted as in your picture)
Then they would click an Edit icon on the row they want to update, then it takes them to an Edit Form either on the same screen or another screen. They would populate it and Submit it and its all simple.
If you need it to be a Grid Style update more than 1 at a time... please let me know but its much more work.