I can't install any application or open Finder.
Whenever I turn on my mac, the finder functions normally. But after a few seconds, the Finder stops working. Whenever I click it again it says “The application Finder can’t be opened.” Then it has a bunch of numbers (-10810) after that. I can’t download any application on it!
4 
1 
Sounds like you have a corruption of some sort. But without knowing which model you have I would be guessing on what you need to do to fix this.
How about plugging in your systems serial number here: EveryMac - Lookup and then telling us which model you have.
由 Dan 完成的
If you can't open the "about this Mac" under the Apple, then get the serial number off the back cover.
由 mayer 完成的
share the screenshot of the error code
由 Amily Grey 完成的