You will not lose anything. The new version installs straight over the old one and keeps every month, transaction, balance and setting exactly as it is. You do not need to uninstall first — in fact you should not, because uninstalling does erase your data.
Find the email you received from Lemon Squeezy when you bought Matrix Budget — the subject line is "Your Sky Matrix Budget order". It contains a permanent download link for your purchase, and that link always gives you the current version.
On the order page, tap the download button next to MatrixBudget.apk. Your phone
saves it to Downloads. If Android asks whether to keep the file, choose to keep it.
Open it from the download notification, or from your Files app. Android will show Update rather than Install, because it recognises the app is already there and signed by the same developer. Confirm, and you are done.
Go to app.lemonsqueezy.com/my-orders, enter the email address you bought with, and Lemon Squeezy will send you a link to your order and its downloads. Nothing to remember and no password — it is the same address the receipt went to.
If that still does not find it, email support@skymatrix.biz from the address you paid with and I will sort it out.
Every build is published with its SHA-256 checksum so you can confirm the file you downloaded is exactly the one I released, and has not been altered in transit.
On a computer you can verify it with
certutil -hashfile MatrixBudget.apk SHA256 on Windows, or
shasum -a 256 MatrixBudget.apk on macOS and Linux. The same checksum is published on
the privacy & security page.
This is the direct-download edition you bought from us, and the app file itself is what you paid for — so it is not left sitting on a public web address for the app to fetch. The app tells you when a new version exists and then steps out of the way; it never downloads or installs anything on its own, and it asks for no permission to do so.
Tap Not now on the banner and it goes away until the next release. The app checks at most once a day, and silently does nothing when you are offline.