It seems like you're looking for help with downloading and troubleshooting Krita 5.2.1 on your iPhone.

Firstly, I'd like to clarify that Krita is not available for download on iPhones as it's a desktop application designed for Windows, macOS, and Linux operating systems. If you want to use Krita on your iPhone, you may need to consider using an iPad or another device with a compatible operating system.

However, if you're looking to download Krita 5.2.1 for Windows, you can find the latest version on the official Krita website. You can follow these steps:

1. Visit the Krita website ('www.krita.org'(http://www.krita.org)) and click on the 'Download' button.

2. Select the Windows version of Krita (32-bit or 64-bit) that matches your system architecture.

3. Click on the download link to save the installation file to your computer.

4. Run the installation file and follow the prompts to install Krita.

Regarding the issues you're experiencing with brush size, I understand that it's not working as expected after updating to Krita 5.2.1. I'd recommend checking out the official Krita forum or community channels for more information on known issues and workarounds. You may also want to try restarting your computer or reinstalling Krita to see if that resolves the issue.

If you have any further questions or concerns, feel free to ask!

Krita 5.2.1 for iphone download