Not an answer to your question, but I have myself started playing with Google Data Studio to make visualizations from both sheets and google fit data, inspired by this blog post:
I’m not an “expert”, but I have some experience. I clicked the link you provided, and saw numerous #N/A! errors on most of the sheets. I also saw many #DIV/0! errors on the Dashboard sheet. If you specify a particular sheet and cell where you would like to start, I could probably point you in a useful direction. Ultimately, I expect you will find that getting the right data in the right cells (either by copy/paste or by uploading a file) will solve most of the problems all at once.
I’ve been tracking my finances for ~15 years using one spreadsheet. It supports everything I need:
monthly credit card bill/expenses tracking
currency conversion
group purchases (e.g. grocery items)
transfers among my accounts
balance for each account
spending categories
monthly averages
You can download this in Excel or Open Document format, if you trust yourself with your data (replication, sync, backups and encryption) more than Google.
Reviving this topic after seeing @Dan_Dascalescu 's post in a different topic. I also track personal finances using spreadsheets, but unfortunately have never found it easy to integrate everything in one place. I have many different files going: one for net worth and financial planning, one for each tax accounting year that is typically heavily edited to respond to the accountant’s specific questions, and one for balances and registers. There is a lot of hand work integrating the different data sources. Over the last two decades I’ve been convinced to start paying consumer SAS vendors multiple times it has always ended it trouble. The typical trouble is: Quicken makes me insane and I stop. But right now I’m actually using Simplifi, which was developed by Qucken, for part of the workflow. I don’t know how to build gateways to the API’s of my financial institutions, so I run these through Simplifi and then export the data for the spreadsheets. Seems really dumb, but it works. Glad to have suggestions that make more sense.