Fix and Improve My Sales Tracking Google Sheet

Description

Hi, I run two flea market tables as a small-scale hobby, and I need an efficient way to track sales to monitor how my business is performing and report the data to tax authorities. I currently use a Google Sheet for this, but it’s not working correctly.
Here’s what I need help with:
Identify and fix the errors in my existing Google Sheet.
Import sales data from a PDF and integrate it into the "Daily Sales" section.
Improve or enhance the sheet to make it easier to use and analyze (or suggest a better tool if applicable).
Provide visual insights, like charts or summaries, so I can track trends and performance over time.
Please check the files I've added below for more context. Parts of the spreadsheet are in Finnish, so you may need to use tools like Google Lens for translation.
While this might be a one-time task, I'm always open to ideas for improving sales and growing this small-scale business. If you find potential opportunities or improvements, there could be more work for you in the future.
The solution doesn’t need to stay in Google Sheets—if you know of a free or very affordable third-party tool that works better, I’m open to hearing your suggestions. Please keep in mind that this is a small business, and I don’t have much extra budget to invest in this.