500 error, link to database cannot be established, please help

[memdaip]

Hi, I am learning hot to create an online shop and I have bought a hosting recently. I tried to install PrestaShop on my computer using FileZilla program and watching tutorials. I transfered PrestaShop install files to my server files ( following every step from the video I found). The next step was to open your website and it was supposed to say that I need to install a new version or something like that. Unfortunately, it said eror 500. I found out how to active debug mode using FTP to check what the probles is. It says ' link to database cannot be established'. I am attaching a screenshot of my screen. Could anyone please help me to resolve it and tell me how to get my website back?