How do I install files and apps in Redmi phone 8?

I know how to install files and apps but my phone randomly shut down and showed the MIUI screen for 10 minutes and when it opened, all data were lost except for yt and TikTok, my phone also can't post photos here, when I download files, it tricks me to wait long but it doesn't even download, also when I install apps, it says to free up spaces and delete games but it recommends 0 games and when I press download it stops the download completely, what do I do??