@louisLS please post in English.

Please check your system / webserver logs for errors. You may also want to set in config_inc.php

$g_show_detailed_errors = ON;

WARNING - SECURITY RISK: the 'show_detailed_errors' config can cause MantisBT to display sensitive information about your system. We recommend to restrict its activation to a Test environment, only for as long as necessary. If possible, do not turn it ON globally, instead limit it for specific user(s) using the Manage Configuration page.

2. Reproduce the error

If the output does not help you resolving the issue and you need further assistance,

3. save the output of the error screen, preferably as an HTML page (not a screenshot !)
4. be careful to remove/mask any confidential information if needed
5. upload the results here

louisLS,

You did not provide any feedback; I am therefore resolving this issue as "no change required".

Feel free to reopen the issue at a later time and provide the requested information.