When you open your *.gform link in Google Drive to access the Google Forms form, you can download the file in CSV format using the File → Download as function in the upper menu. This is good if you want only the text data from your forms.
Convert Link to Google Forms web application form document to Comma Separated Value.
We have found one software suitable in our database for this conversion.
On-line services software - convert gform to csv on web
A form making web app from Google
Convert from gform file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.