I can understand the problem you are having its because you have translated the URl's too. For Example: https://wordpress.madinsk.fr/Formations/gestionnaire-de-paie-option-comptabilite/ you have changed Courses to Formations. In this case you have to do some customizations into the theme as well.
Please send me your wp-admin/ and FTP logins i will apply the required changes so everything works well with your new Custom post identifiers.
First of all Please oepn the file wp-content/themes/education/lib/admin/metaboxes inside metaboxes you will find the file >> page-layout.php please edit this file, and replace line on 31 which is
'pages' => array('post', 'page', 'courses', 'teachers', 'events'),
Replace this line with
'pages' => array('post', 'page', esc_html__('courses', 'education'), esc_html__('teachers', 'education'), esc_html__('events', 'education')),
Now you will see the Page layout options in your events, teachers, and courses for Education WordPress theme. Now you are not having proper display of Teachers, Courses, and events. Which means as they should be displayed they are not being displayed. In their single event, single teacher, and single course views. Now you have to copy and rename some files. Please do not delete original files in case later updates you do not get into any tourble. Also by updating above code your future updates will not be effected because i have added this fix into theme which will be released with next update.
Now in your wp-content/education/ Copy These files or make their duplicate.
1) archive-courses.php add it with name like archive-Formations.php << Please note you have renamed Courses to Formations and F is capital so file should also have first letter capital.
2) Now do same with these files what you just did above. archive-events.php, archive-teachers.php, taxonomy-courses_group.php, taxonomy-events_group.php, taxonomy-teachers_group.php Please leave the original files as they are just make a new copy of those files and rename them accordingly. This way your updates in future will not be effected.
Yes this Education WordPress theme is 100% translation ready and compatible to WPML completely. You can also run multi language sites with Education WordPress theme easily if you have any problem you can always get back to us.
Why its to make changes into theme. 1st code suggestion is actually bug in the theme which will be fixed when you add the new provided code for page or post layout. 2nd duplicate of files, that's because you have changes the slugs of post types means changed the urls most of themes does not offer changing the slug that's why they do not require new files addition. But we believe everything should be in 1 language from Page URL to everything. Thanks if you cant figure out how to, just send FTP we will do that.