Mr Marco – you need to access the site files for WP on your server, either via your control panel at your web host, or via FTP software. I use FTP software, go to the wp-content folder and right-mouse click it and scroll down to Properties, or some programs it says Propertes/CHMOD and change the permissions to 755 (some programs it may need to be 777). That’s it.
The above concept is the same within your hosting cpanel, only you would change permissions from within your File Manager – just click the wp-content folder to select it, and usually to the right, you’ll see a list of options appear and choose to change the folder permissions to 755 (or 777 if you must – not usually recommended).