Turning makes a moaning sound

[Regulus]

Lately the car has been making a moaning sound sometimes, when I turn left or right. Usually in low speed, and especially if I hadn't been driving it for a few days.
I can't say I have heard it when I when I have been driving for hours.
I noticed the mineral oil reservoir level had dropped a little.
A little under half between min and max. So not very low.
I filled it up thinking that might be causing it.

There is a leak on the left side of the car. I saw that when I had the front wheels off. I suspect it must be the steering wheel pump.
As there is so much oil on the car, I guess that is why I didn't see a big puddle under the car. See photo.

Now I am worried that I will be embarrassing everybody if my car starts moaning in every turn I make