Solved blanc page after safe as copy a category

Hi Guys,
I have a category that I want to safe as copy. see pic. after doing this the whole kunena display in frontend is off and backend is broken, for ex I cannot open categories in dashboard anymore and some more probs. What am I doing wrong? This is a very ussuall procedure in joonla to safe as copy. why here in kunena it does not work?
regards, martin

Sorry, I'm not able to reproduce this problem. Summary of your topics:
You get a blank page if you want to install Kunena
You get a blank page after safe a copy of a category
You get redirects to your hoster in the backend menu items and categories
I've noticed in your configuration report "Max execution memory: is -1". This should be a minimum 32M not a minus value.
docs.kunena.org/en/basics/requirements
Check also the folder permissions. By default Kunena will install with 755 and 644 permissions for folders and files respectively.

Dear Rich,
thnx. I changed the memory limit to 512MB, you can check this here: www.psychoanalyse-muenchen.de/phpinfo.php
I checked the permissions: all the folders have 755, this should be ok and I havent changed anything anyway.

I try to explain again:
Imagine you want to create a new category. So you go to backend>kunena>categories. There I opened one category and tried to safe it as copy, then it loads a long time and finally it comes to this path: www.psychoanalyse-muenchen.de/administra...nena&view=categories . view see img
I tried to create a new category, I clicked on safe button and again the whole system breakes down.

In frontend the forum looks like this: see img "url.PNG"

I went to database, deleted the kunena category table and inserted a backup of this table, then it works again but with same errors like above, means i cant save the new categories (and maybe even more things dont work...)

First go to Extensions -> Manage -> Database in the backend and check whether everything is OK.
Then to Joomla Global Configuration (tab Server) and set Error Reporting to Maximum. Afterwards try to create a new category. Maybe you get an error message which can localize the error.

Supplement:
This is only a vague guess. I've searched here in the forum and found only a second user which uses php 7.2.28. Admittedly he has not the same problem, but in the broadest sense a routing problem.
Is it possible for you to switch to another php version to test?

thnx.
I checked database already before and again, everything is ok.
I also changed php Version from 7.2 to 7.3., no change.
I set error report to maximum and now I dont have access to backend anymore, just I have a blnc page with this information:

Warning: ini_set(): A session is active. You cannot change the session module's ini settings at this time in /homepages/33/d134278986/htdocs/psycho2020/libraries/joomla/session/handler/joomla.php on line 48

Warning: Cannot modify header information - headers already sent by (output started at /homepages/33/d134278986/htdocs/psycho2020/libraries/joomla/session/handler/joomla.php:48) in /homepages/33/d134278986/htdocs/psycho2020/libraries/joomla/session/handler/joomla.php on line 112

Warning: session_name(): Cannot change session name when headers already sent in /homepages/33/d134278986/htdocs/psycho2020/libraries/joomla/session/handler/native.php on line 128

Warning: session_cache_limiter(): Cannot change cache limiter when headers already sent in /homepages/33/d134278986/htdocs/psycho2020/libraries/joomla/session/handler/native.php on line 235
Error: Failed to start application: Failed to start the session because headers have already been sent by "/homepages/33/d134278986/htdocs/psycho2020/libraries/joomla/session/handler/joomla.php" at line 48.

I will try to reset this and be back
regards, martin

I do have another idea. Can I backup whole script and delete kunena complety, then make new installation and then insert the former database table for not loosing all the content?
I tried to set error report to simple but also then I get only a message on a blank page and I cannot return to joomla backend.