Should points of a left-side navigation bar be single line with ellipsis or multiple lines?
I have a strong opinion that single lines are preferable, because eyes are reading first words/characters in every line, and second lines distract from this process.
Your users will not want to navigate to the page just to find out what the title is.
If I saw "Practical En...", I would not know what that page is.
I'd rather have more space dedicated to navigation so I could read the full titles.
There are many patterns for navigation out there and can be found with some web searches, but they can vary greatly depending on your target device and platform.