Clearly message tells PHP cannot write in folder projeqtor/tool
If rights are correctly set (as you decribe it) then possibly an external tool locks access (antivirus or selinus)

Thank you for your answer, but in fact the parametersLocation.php file does not exist in projeqtor/tool
I just looked at it.
chmod chown I did it twice.

PLEASE WRITE IN ENGLISH

Of course parametersLocation.php does not exist.
PRojeqtor tries and create it, and this is this write that fails.

All right, I'll see if there's a way to force it when I have time.
Thank you for your availability.

Be very careful: the use of -R commands creates many problems in Debian/Ubuntu systems and I had some very big problems. Do not try to install projectqtor if rights issues arise.

Be very careful: the use of -R commands creates many problems in Debian/Ubuntu systems and I had some very big problems. 

Of course a

chmod -R 777 *

at root lefet whith root rights (connected as root or with sudo) will "kill" your OS (won't work anymore)
Same think for a

chown -R www-data *

The most dangerous is to start location with a /

sudo chmod -R 755 /var/www/html/projeqtor

Because if you enter a space after the first / you'll aplly it at root and kill your system.
This is not linked to projeqtor, nor to admin rights, but basic of administration of Linux OS.

Do not try to install projectqtor if rights issues arise.

Rights issues are easy to solve in most cases.
Of course it requires minimum knowledge of linux system to enter correct line commands.
Or you should use Linux GUI to apply changes from visual interface.

I only did:
chown -R www-data: /var/ww/ww/html/projeqtor/files and chmod -R 755 /var/ww/html/projeqtor/files
as you had recommended and I had some problems.
I am not questioning the software, which is certainly very interesting.
I suggest that you provide details of safe installations on the main systems to avoid problems for those who want to test it.

If these command come from forum, there is a great issue : they should work on no system
Correct commands are

chown -R www-data: /var/www/html/projeqtor
chmod -R 755 /var/www/html/projeqtor

But I would suggest to rather use

cd /var/www/html
chown -R www-data: projeqtor
chmod -R 755 projeqtor

This assumes that :
1) /var/www/html is the DocumentRoot defined on your apache configuration file
2) you installed projeqtor directly on this flder, without whanging name of top folrder (projeqtor)