Help With Cumulative Line Chart Showing Year Over Year Sales Growth

OK, now that's a measure problem. You need a YTD cumulative measure.

The shortest solution is probably

TOTALYTD (  SUM ( 'deal list'[Deal - Value] ), 'DateTable'[Date] )

but I'm not a fan of built-in time-intelligence functions.

There are lots of ways of writing a TOTALYTD without time-intelligence. For example, a pattern like this one here:

Month-related calculations – DAX Patterns

Or you can use the newer WINDOW function and write something like this:

Amount YTD =
CALCULATE (
    SUM ( 'deal list'[Deal - Value] ),
    WINDOW (
        1, ABS,
        0, REL,
        ORDERBY ( 'DateTable'[Date], ASC ),
        PARTITIONBY ( 'DateTable'[Year] )
    )
)