Have a lifting system installed?

Can someone give me advice regarding a lifting station? We are building with a basement. The ground floor is at street level. The basement will be purely a utility basement, wastewater only comes from the washing machine and the sink. We have pressing water in the area, so the basement will be constructed as a "black tank". My parents and parents-in-law each have a lifting station. The general contractor has now offered a small one ("Kleinhebeanlage Arma-Drainer-Box or Sanifix"). Is it advisable to take a small lifting station or rather not? According to which criteria do I decide that?

The question is: For what?

I have installed two systems in the basement - one is a sump pump that collects the wastewater from the washing machine, two hand basins, shower, air conditioning condensate, and heating overflow. And possibly also minimizes flooding...

There I installed two submersible pumps, which are fail-safe and back each other up.

And then I have the classic toilet lift, a Sanibroy. It only pumps fecal matter up and is located in the room next to the bathroom.

For you, I would also only install a sump with pumps, but no ready-made lifting system.

Or is it also about the issue of the backwater valve?

Yes, exactly. The question is: for what? Do I even need anything or can I save myself all that stuff? When do you use something like that and when not? A backwater valve is also a topic. I’m not familiar with that area at all and don’t know what I should plan for, or whether I even need any of it.
There was once a case where it rained so heavily that the sewer system could no longer absorb the water and it pushed up through the drains onto the street (but that must have been about 15 years ago).
Does the lifting unit have anything to do with that, or do you only need the backwater valve for that and the lifting unit is only to pump water below sewer level into the sewer?

Lifting system used to raise wastewater / sewage generated in the basement to the sewer level in order to allow it to flow away normally with a slope.
Backflow valve is used to reduce external impacts (sewer blockage or unwanted guests such as rats).

If there are no toilets in the basement and / or none are planned, submersible pumps (for redundancy reasons two pumps, preferably on two different circuit breakers or circuits, and floats at two different heights) with a pump sump are more cost-effective.

There are mechanical and electrical backflow valves.
Mechanical ones are cheaper but over time do not close properly due to deposits and can fail when needed.
Electrical ones are expensive, open and close at certain intervals to remain operable, require electricity, and should be easily accessible. How they react in the event of simultaneous flooding and power failure, I cannot say.

The flooding combined with a simultaneous power outage would be a deal breaker....