@Nightowl @Marcos
The thing that worried me was that when I tried to find where the file came from, I found two suspicious websites. I don't know between these two suspicious websites, which website sent this file called "Android/Packed.Jiagu.K (variant)". Both websites have many different addresses and the addresses are very long.
Before I found a suspicious file on my phone, I thought these two websites were normal advertising websites and I immediately clicked the back button if an advertising website appeared before the website was fully opened. But after I checked the two websites using Google Transparency Report (https://transparencyreport.google.com/safe-browsing/search?hl=en), a warning appeared that the two websites were dangerous. The results of the check are written like this:
"Some pages on this site are unsafe. The site https://*************. ***/xxxxxxx contains harmful content, including pages that:
• Try to trick visitors into sharing personal info or downloading software".
Okay, thank you. I will send an email containing the name of the file and some of the suspicious website addresses. I don't think it's good to display the website address here because I don't want to make the person who sent the suspicious file to my phone feel happy and excited.
Thank You Very Much for the help from both of you. ☺️