Any idea what these 2 apertures are at the base of the window? Are they vents? If so don't see how they work as there's nothing corresponding on the inside of the window....
...the drainage holes have lost their cover caps - if you care for the aesthetics, something like these may be suitable replacements, but check the sizes:
uPVC seals stop most of the rain entering the frames but the black silicone seals are not perfect (by design). The holes are there to let rain water drip out.