Never buy a used PC., You don't know if it was abused or ever cleaned or updated the operating system. That particular one doesn't look like it has very good airflow either. Used means no warranty.
If in doubt go with a prebuilt Descktop from HP, Lenova, Alienware Europe. Or even NZXT in Europe. You pick and chose the parts that you can afford https://nzxt.com/news/nzxt-prebuilt-pcs-available-now-in-europe. Sit down with someone who knows about computors to help you choose. Also stay away from Ebay and Facebook. and always pay with Paypal. They will help you out if you get screwed over.