Sealing floor-level windows

Hello everyone,

I will start with the outdoor facilities soon,
and I noticed that the ground-level windows from the outside are not sealed, see picture.

How can I best make them watertight?

Thank you very much in advance

Regards

Why you? Are you building with GU/BT? Or with an architect? Actually, it should be the responsibility of some trade; for us, it was the structural builder who also did the masonry waterproofing.

In case of doubt, as described in the execution details - although that is, of course, somewhat heretical.

There is a sealing in this area, which was installed by the window maker.

Normally, that is the task of the window installer, with what do you seal the windows at the bottom, with a sealing tape? Or with something liquid?

Normally, the roofer does that ;)

And now you can no longer seal it properly without further ado, because the plaster has to be removed on the left and right so that the sealing can be connected to the masonry with its sealing.