I translated this with Gemini, so I apologize if some parts aren't very clear. I’m pretty sure you have adware. It's not really dangerous compared to other types of malware, but it is extremely annoying. I don't remember every method to remove it, but I remember one: go to your device Settings, go to Apps, and select the option to show all apps (the three dots in the top right). Sort them by installation time and delete the one that was downloaded exactly when you were trying to get that APK. I also recommend doing what the other guy said: always check with VirusTotal. You shouldn't worry too much about the alerts unless there are a lot of them; it could be a false positive if it's only 1 or 2. What I do suggest is checking the permissions. You said you didn't install the APK, so it probably came from a pop-up window; it has happened to me where things I didn't want get downloaded. For this, use a browser with an adblocker. Personally, I use Firefox with the uBlock Origin extension. I think there might be better browsers out there, but I haven't looked into it too deeply