The following error appear:

Critital error 01: There is no write permission in XX/

Solution:

Using a ftp programs or Windows Explorer access to your FTP, right click on the folder (XX/) 
you should see CHMOD or File Permissions or something similar, set it to 777

The following error appear:

Critital error 02: Max. image size (XXMb) is greater than the value in php.ini (XXMb)

Solution:

In config.php their is a variable allowing you to choose the max size of the uploaded file.
Unfortunately, your webhost set a limit, when you receive this errror, it only means that the value you set is higher to the server value. In other words, you must change it.

Open config.php

Find : (Where X is the value you set, by default it is 2)

$max_mb = 'X'; // Max. image size (Mbytes)

Replace X with a lower value, if you still get the error, try again with again a lower value.

The following error appear:

Critital error 03: You must load the GD extension.

Solution:

Unfortunately, your web host didn't include in their PHP libraries the GD library.
Their 2 way ways to fix it :
1 - Ask your webhost to download it and include it (Web hosts always reply with a negative answer... but you can try)
2 - Find a new web host.

Sadly, their is no other ways to fix this error.

The following error appear:

Critital error 04: Invalid $DOM_SCRIPT, edit it manually in config.php

Solution:

In config.php their is a variable telling Chevereto what is your Website url. For some obscure reasons,
Chevereto can't find it.

Open config.php

Find : (Where X is the value you set, by default it is 2)

$DOM_SCRIPT = $_SERVER['SERVER_NAME'];

Replace with:

$DOM_SCRIPT = 'http://yourwebsite.com/chevereto-path/';

Where cheveret-path is the subfolder of your root where you uploaded chevereto,
if you uploaded chevereto to the root of your web directory (www or public_html (or something similar))
Replace with:

$DOM_SCRIPT = 'http://yourwebsite.com/';

The reason of this error to appear can be because you are using a sub domains, in this case it will be similar to:
Replace with:

$DOM_SCRIPT = 'http://sub.yourwebsite.com/';

Again if you uploaded it in a sub directory of the sub domain don't forget the '/chevereto-path' ...

The following error appear:

Critital error 05: You must load the cURL extension.

Solution:

Unfortunately, your web host didn't include in their PHP extensions the Curl one.
Their 2 way ways to fix it :
1 - Ask your webhost to activate it and include it (Web hosts always reply with a negative answer... but you can try)
2 - Find a new web host.

Sadly, their is no other ways to fix this error.