MySQL error [2006] "server has gone away"

Hello, I hope someone can help with the following issue.
I am not able to install projeqtor on my linux server. I have installed the LAMP stack (linux, php, mysql) and the projeqtor data is uploaded to the correct location.
Also the projeqtor configuration screen shoes up for the first start when entering the server address in the browser.
After entering all relevant data / parameters and clicking on "OK", a small rotating circle appears indicating it is loading. Then after approx. 50s it stopps with the error message "server has gone away". I googled already for a solution and modified all possible timing limitations which I identified (in the mysql config file: my.cnf file). I.e., max_allowed_packet, innodb_log_wait_timeout, net_read_timeout, net_write_timeout, slave_net_timeout, thread_pool_idle_timeout, connect_timeout, innodb_log_file_size.
The issue still remains.

Can someone help?

Thanks in advance, Wolfram.