To retrieve the answer for each row on grid questions, you have to use a specific syntax.

Type: <<Your question title [row label]>> in your template for each existing row.

For example, let's say you have included a multiple-choice grid with the question 'How much did you like the conference?' in your Google Form.
The subjects/questions are displayed in a row ('The topic', 'The premises' and 'The speaker'), and the corresponding answers 'I loved it', 'I liked it', 'It was alright' and 'I did not like it' displayed in a column:

In your template, write:

• <<How much did you like the conference? [The topic]>>
• <<How much did you like the conference? [The premises]>>
• <<How much did you like the conference? [The speaker]>>

Where 'How much did you like the conference?' is the question title, and 'The topic', 'The premises' and 'The speaker' are your row labels.

Note the blank space between the question title and the row label. It is the same syntax used to display grid results on spreadsheets.

And here is the result in the generated PDF file: