ᐅ Water drainage in front of L-shaped retaining walls and garage – water accumulation

Hello,
our lawn has a slight slope and ends at the garage and L-shaped retaining walls. The water cannot flow further downhill there.
See the picture. Water cannot flow downhill anywhere else either; it is a dead end :-(
Anything that does not soak into the clay soil accumulates there.

Due to the structural layout of the house, garage, parking space, and driveway, it could not be done differently!

There is a drainage pipe in the lawn at about 50cm (20 inches) deep, but it does not run “across” the garage / retaining walls, rather along the slope (yellow, see picture).
At the bottom near the garage and the retaining walls (height 270cm (106 inches)) there is a drainage system, but this is installed quite deep, and water soaks through too slowly to reach it.

I would now like to divert the “accumulated” water at the end into the existing drainage or sewer connection (in the red circled area).
(There is a core drill hole in one of the retaining walls at 50cm (20 inches) deep where the pipe leads down to the sewer, see separate picture).

But how?
Should I install a new drainage pipe quite close to the surface (10cm (4 inches) deep) along the retaining walls and the garage? Would that help?
Or something like a drainage channel that has side openings so water does not have to flow in from above?
Or remove the lawn in that area and lay a 50cm (20 inches) gravel bed with a drainage pipe inside?

What would you do, any ideas?
Thanks!