Sorry, just fyi... I'm not trying to be a dick...
And I don't know it all, and definitely don't wanna sound like I'm being condescending or anything...
So... I hope none of this comes off like that...
Just trying to be helpful....
Anyway... for clarification purposes...
I'm not sure what you mean by they "deleted the file manager to your apps"... A file manager is a application used to transfer files from your computer to your host.
Usually, the "file manager app" is located on your host's control panel somewhere? (cPanel maybe?)
Are you sure they deleted that app off your control panel? I'm guessing you could ask them to put it back if that's the case...
Maybe get Hostinger to "factory reset" your site to a blank slate to be safe if it's feasible. So you at least get a "Page under construction" or something loading when you visit it...
If you really have no file manager, and they won't put it back... You would have to follow the steps I mentioned above and install an alternative file transfer solution to your computer...
Or, did you mean they deleted the directory or folder your apps were stored in? If that's the case, just upload your files back there... My 'web page' folder is called public_html for instance... Log into your host's control panel, find the file manager app... It should be in there somewhere I'd think... and transfer your files... Otherwise, use the software I mentioned above and transfer the files that way....
More technical stuff follows... But you gotta get past uploading your files first.
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
I don't use Hostinger, so I can't be very specific... but...
Like ouga said, make sure you have right right php version configured. I think a lot of panels use 7.2, or 7.4 maybe, but don't hold me to that... I'd avoid version 8 anyway...
Basically, you just upload the files to your host... But, again, like ouga said, it has to be configured properly... I thought Hostinger took care of that, but I could be totally wrong for sure... Wouldn't be the first time...
After that... some panels use "Source Guardian" or ionCube... so, those might need to be installed for some. Although that should be apparent when you try to visit the site. (ie: The page will usually say, I need sourceguardian or ioncube installed.)
Some dependencies I use are: (I dunno if I'm missing any or if all are needed...) As I have different setup and am just learning myself...
apt-get install php7.2-{cli,pdo,fpm,zip,gd,xml,mysql,cgi,sqlite3}
apt-get install php7.4-{cli,pdo,fpm,zip,gd,xml,mysql,cgi,sqlite3}
apt-get install php-curl php7.2-curl php7.4-curl php-gd
Proper permissions on files and directories always helps... .htaccess file?
Read the read.me file or .info or whatever may be the case for instructions. (I probably should have put that first, lol) RTFM... hehe
Anyway, good luck!