SUM transactions text fields if contains specific campaigns Analytics+DataStudio

I’m pulling data directly from Google Analytics, but I only want to add transactions from specific campaigns or source and medium

Here is the test in DataStudio: https://datastudio.google.com/reporting/2ad4ab07-b7a2-4f0a-b84e-65f043da9afd

I don’t have a spreadsheet because the data is directly connected between DataStudio+Google Analytics

I have a total of Ecommerce transactions, example. That total is on a bar chart. On it I’m trying to add 2 lines:

line 1: transactions of organic source (total 60)

line 2: transactions of paid media source and campaign (total 40)

the two lines sum gives the value of the bar (total 100)

However, in DataStudio it is not possible to add separate filters. If I add a filter will filter the entire chart, the 2 lines and the bar, because all metrics are the same: transactions.

So I thought about creating metrics with the formulas. I tried CASE, WHEN and SUM, but DataStudio says I’m mixing text with numbers.

I tried:

transactions of paid media source and campaign

SUM(CASE
WHEN REGEXP_CONTAINS(Campaign,"PMAX*") THEN Transactions
WHEN REGEXP_CONTAINS(Campaign,"Smart Shopping*") THEN Transactions
WHEN REGEXP_CONTAINS(Campaign,"Shopping - Catch All*") THEN Transactions
WHEN REGEXP_CONTAINS(Campaign,"Discovery*") THEN Transactions
WHEN REGEXP_CONTAINS(Campaign,"Trueview*") THEN Transactions
WHEN REGEXP_CONTAINS(Campaign,"Bumper*") THEN Transactions
WHEN REGEXP_CONTAINS(Campaign,"VideoAction*") THEN Transactions
WHEN REGEXP_CONTAINS(Campaign,"GDN*") THEN Transactions
WHEN Source/Medium="google / cpc" THEN Transactions
ELSE 0
END)

or only source medium

CASE
WHEN Source/Medium="google / cpc" THEN SUM(Transactions)
END

not work

here are the images:

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Thanks in advance for all help!