You can create a php info file in order to check the current values and check which is the php.ini file in use. Create the following file in your public_hmtl folder - phpinfo.php and put the following code inside it:
You can also use the following command in order to find the location of the php.ini file:
php -i | grep php.ini
The output will be:
Configuration File (php.ini) Path => /etc/php/7.2/cli
Loaded Configuration File => /etc/php/7.2/cli/php.ini
Then check for the current value of memory_limit you can also check which is the configuration file - php.ini that is currently used and apply the changes there (if the site using the global php.ini file and you change the values for these settings this will make the changes globally for all sites). Ideally you would like to have the following values:
memory_limit = 256M
You also need to restart your web server in order the changes to take effect.
Hope that this helps!