multilanguage portfolio languages showing both languages issue

i have got an multilanguage wordpress site with no additional pluggins

Hi plastikelectrik,

I’m not sure if you can get a multilanguage site without no additional plugins.
Or probably you have it installed before and then deactivate/remove it ?

If so, then you need to install it back in order to get things work as before.

For this,

also it is possible to get to an older state of the wordpress to get rid of that fail

then you need to create a backup of your site before making any changes (editing files, creating entries, etc.).

To understand about WordPress backup, you might want to start from here:
https://codex.wordpress.org/WordPress_Backups

or if you want to skip the hard stuffs, you can always look for backup solution/alternatives in:
https://wordpress.org/plugins/search.php?q=backup

Here’s another link that might help you in choosing the best for you:
http://www.wpbeginner.com/plugins/7-best-wordpress-backup-plugins-compared-pros-and-cons/
https://premium.wpmudev.org/blog/free-quality-backup-plugins/