You are going to have to take the time to follow emsr2d2's advice.
I've just rattled through a bunch of examples in my head, and it would take pages to cover everything.
They are synonyms, but that does not mean they are always exchangeable.
We just don't say, "I want to widen my awareness". We do say, " I want to broaden/expand/extend my awareness", but each choice has slightly different meaning.
A company can expand or extend its reach into a new market, but it would broaden or widen(?) its reach in an existing market (probably). Note the "?"; not a great example.
"Broaden" can mean the same as "widen" (to make something wider, like a road), but broaden can also suggest "diversification".
"Expand" can mean "diversification", but can also simply mean "more".
"Extend" can mean "more", but can also mean "further".
See what we mean?