Why my function.php file in theme delete automatically?

I was using electro theme. and that was going fine I add some code for woocommerce order cancellation in the function.php file of the theme. after that, my site shows an error that “There has been a critical error on your website.”.
when I checked my Cpanel… I found that the function.php file of my theme is missing. I have the site on the localhost and that’s is going well. I uploaded function.php file from my localhost theme into the Cpanel, my site runs perfectly but for just 7-10 sec.. after that, it is showing the same error and when I check Cpanel I found that functiono.php is missing again..
I uploaded it again but that got delete again..
I uploaded the whole theme again but got the same issue.. then I uploaded the whole wp-content folder but still the same issue that function.php got delete automatically. then I uploaded the whole site from the localhost and connect it with the database but still, I got the same error..
I set debug to true and I got these errors you can see in screenshotenter image description here

kindly help me in solving this issue