…cannot understand this: “f you are unsure which Windows version you have, press ⊞ Win+Pause to open your system properties window. The LibreOffice Main Installer download page can be selected with a built-in help file for your language” as I have no idea what on earth to press…? or where…?
The Installation Instructions for Windows page helps you to decide which install package to download. There are two packages for Windows available: 32-bit, and 64-bit. Which one to choose depends on what architecture of operating system you have: there are 32-bit and 64-bit Windows. So in case you don’t know which one you have, the instructions tell you what to press on keyboard (it means, you need to press Windows key + Pause key), to see your operating system architecture.
Then the Instructions page proceeds, telling you that below are the links that you can use to open main installer page, on which the chosen package will be pre-selected, and also a help file with the language of your choice…