I tried blowing the picture up and it looks like the frame of the door ( at the bottom ) does not meet the side strutt, therefore, the water goes around this and through the little gap. If this is the case and you'd need to take a close-up pic, then it's a design fault and i'd send the shower enclosure back to the manufacturer. There would be no way of closing the gap unless you made a piece of rubber of plastic fit the gap and glue it in place then mastik it.

If the scratches are not too heavy you could try this; https://www.youtube.com/watch?v=JErQ72NH4jA this video has very clear simple instructions. Amazon UK sell cerium oxide glass polish, use a 2 speed cordless drill, to start, stay on the slow setting until you get used to it then go to the higher speed. Make sure to keep it wet for cooling.

You can add a return panel, to act like a door and keep the space more enclosed to reduce splashes. I have one in my en-suite. I am pretty sure you can add one to an existing fixed shower enclosure. They're not that expensive.

Kartners is indeed a reputable brand known for high-quality bathroom accessories, including shower glass door hinges. Their products are well-regarded for their durability and design, available in a variety of finishes such as polished chrome, brushed nickel, and matte black, which can complement different bathroom styles If you're looking for alternatives, you might consider suppliers like Shower-Glass.co.uk, which offers a range of high-quality hinges. Another option is Bohle, which provides a variety of shower door hinges with different mounting and finish options, including chrome and stainless steel..