Hello! Sorry this is overwhelming you but I bet you can get through it.
What I would suggest first is trying out this Velo package as is - get the demo form hooked up to a google sheet and test it out. That way you can see how the interaction works and then modify the code to connect to your form elements instead.
To add a Velo package to your site, click on the {} on the left hand navigation with dev mode on
Under Packages > Velo > Install Velo package
Search for google sheets integration
Once the package is installed, follow along in the README file in the package and see how far you can get. Post any code specific questions to the forum if you get stuck.