Have a look at lof files : projeqtor log file or php log file or apache log file.
Sure you have a Timeout.
Change your max_execution_time in PHP config file.

I set the variable max_execution_time = 0, but the behavior is the same as above.

I set the variable max_execution_time = 0, but the behavior is the same as above.

di you restart PHP after update of php.ini ?

yes... 🙁

So look for errors in Apache error log file or in php log file.

in Apache error log appears: PHP Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 32768 bytes) in Unknown on line 0, referer: http://localhost/projeqtor/view/main.php

So it is memory that is too small.
Try and extend memory_limit in php.ini

I tried also with 8000M but it doesn't work ...

and error is ?

PHP Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 32768 bytes) in Unknown on line 0, referer: http://192.168.12.137/projeqtor/view/main.php

And you need me to explain tthe error ?
Read it !
536870912 is 512M

I have read and tried also with 516M the same error always appears

But then could it be a bug?

I have read and tried also with 516M the same error always appears

If 512M is not enough, I don't think 516M will have chance.
Try 4G, and restart PHP.

But then could it be a bug?

I don't think so.
But there can be some inconsistency that leads to non ending loop.
Try and Check for inconsistency (in administration screen)

I also tried 8GB

Please try again wth 8G and show error ...

Something is changed. Indeed there were errors of consistency that I set with the appropriate button. Now the errors are these:

[Thu Oct 03 14:56:36.728647 2019] [php7:error] [pid 2774] [client 192.168.12.1:62240] PHP Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 36864 bytes) in /var/www/html/projeqtor/model/PlannedWork.php on line 665, referer: http://192.168.12.137/projeqtor/view/main.php

[Thu Oct 03 14:56:36.734946 2019] [php7:error] [pid 2774] [client 192.168.12.1:62240] PHP Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 32768 bytes) in Unknown on line 0, referer: http://192.168.12.137/projeqtor/view/main.php

Hi,

Try and change Global Parameter "Memory for PDF generation" (on tab system).
I did not expect this parameter to be used for planning, but it"s worth a try.

I have set et 8000 the global variable and now appear this :
[Thu Oct 03 16:37:40.348001 2019] [php7:error] [pid 3463] [client 192.168.12.1:63100] PHP Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 20480 bytes) in /var/www/html/projeqtor/model/persistence/SqlElement.php on line 3016, referer: http://192.168.12.137/projeqtor/view/main.php
[Thu Oct 03 16:37:40.354904 2019] [php7:error] [pid 3463] [client 192.168.12.1:63100] PHP Fatal error: Allowed memory size of 536870912 bytes exhausted (tried to allocate 20480 bytes) in Unknown on line 0, referer: http://192.168.12.137/projeqtor/view/main.php

thank you very much for your kindness and patience

where can the problem be in:
/var/www/html/projeqtor/model/persistence/SqlElement.php on line 3016 ???

The line is not important as it is memory issue.
The issue occurs when memory is full.
If you change few things on projects, issue will occur at different location.

Your issue is that your parameters are not taken into account : memory limit is always 512M and you need more to plan all the projects in one shot.

So how can I do it? Can't create many projects? is it a bug?