Newbie here with some basic questions (dictionaries, AutoCorrect, built-in offline Help)

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Hi. Your first question is the hardest but lets see:

1. There isn't a Look Up word function. If you have a dictionary with a thesaurus installed then you can right-click on a word and see some synonyms. Not exactly a definition but helpful. I would be more inclined to choose my reference source and search in a browser. Once upon a time there was an OOo extension which included such a function. I don't know if it still works but you can try and see: https://extensions.openoffice.org/en/...
2. Auto completion. In the menu click Tools | AutoCorrect | Autocorrect Options... In the window that opens click on the Word Completion tab, untick the box labelled Enable Word Completion
3. Help. Go to https://www.libreoffice.org/download/... , in the box that contains the LO version you installed is a suggested help pack to match your language and OS bits 64 or 32. If that isn't the one you are after then the line below says "Need another language?" Follow that link to select the pack(s) you want to download and install.

Cheers, Al