Mixing metrics with dimensions (counif)

[MikhailArt]

Hi everyone!
I'm stucked with a problem.

I have connection to GA4 data with default dimensions and metrics.

I need to make a table of 3 metrics:
1. active_users
2. users_form_submit (active users with event_name="form_submit")
3. conversion (users_form_submit /active_users )

The formula for users_form_submit would look something like this,:
SUM(CASE WHEN Event name='form_submit' THEN Active users END)
- but I get an error 

Unfortunately, haven't found solutions for such case in web, except for scorecards. But what if I want to make breakdown by source/campain/etc?
Hoping for your help.