Signal app ignores system settings

Hi all, I am using signal 5.35.3 on /e/OS latest 0.19 stable on Samsung S7
Signal eats a lot of battery and I´d like to send it to sleep in an easy-to-do-way (no endless clicking through system settings) whenever I don´t need the app.

But it seems like signal ignores all the system settings that I found and tested up to now (not 100% sure about the english wording, German is my system language):
According to privacy and other settings in my phone signal is

  • not allowed to stay active
  • not allowed to work in the background
  • not allowed to use data in the background

nevertheless it works (receives messages immediately) and uses battery even though the app is closed - but it shouldn´t - or am I wrong?
My expectation was that with these settings signal will only work when it is open.
But the only way to stop signal from working and using battery power seems to be a forced shutdown (app-settings in system settings)

I couldn´t find anything helpful so far, can anybody help?
I´d appreciate any insight in what goes wrong here or where I am not getting the point :slight_smile:
(did I make my point clear, any info missing?)

edit: typo+improved description