Hydraulic oil loss

Again Moin from me to the community ;-)
I just remembered something that hurts my stomach. I know remote diagnosis is always difficult to take, but perhaps there is a child's disease in this regard.
I have to refill hydraulic fluid regularly. Sometimes the red exclamation mark (probably due to the loss of pressure in the brake or the use of the brake) is used. The Commission's proposal is a very important one, and it is a very important one.
As far as I've heard, the hydraulics from the steering system support the braking system?!. When the engine ran I have after some service life an oil stain under the car and when I drive, it squirts and stinks after stopping from the left wheelhouse. Has anyone ever had the same problem?! You can't see anything from above and from below I can't see the affected spot either
LG Kai