Basic Line Chart Setup with Multiple Lines Grouped by Month

I find that many charting questions really end up being spreadsheet questions -- such as your case. Currently, the data are very poorly arranged in the spreadsheet to give the kind of chart you show in your picture. By far the easiest way to achieve the chart you want will be to rearrange the data in the spreadsheet. Once you get the data properly arranged in the spreadsheet, creating the chart should be straightforward (see this essay for a detailed explanation: https://peltiertech.com/good-chart-data/ ).

Rearranging the data probably needs to begin by understanding if this is the raw data or if this is a summary of a broader database of data. If this is the raw data, there could be value in considering some kind of "unpivot" operation to make a good database that will make future manipulations a lot easier. If this is a summary of a broader database, then it might be easier to start with the database query and make changes there to get a better arrangement.

So, without getting into specifics, yet, what can you tell us about where this data comes from, how it gets into this spreadsheet, and what changes you are allowed to make to how the data is arranged in the sheet?