Custom CSS not working

Hi, after trying to alter the css with the embedded own code input without any success, I looked inside the source code:
and it seems that the code block with altered custom code is placed before the general css links. So it’s been overwritten.
Or am I dooing something wrong?
Any chance to get it done in the next couple of days? I have an urgent client task running… ??
Thanks in advance

https://www.ads-software.com/plugins/shortcodes-ultimate/