"Crash into" is not a phrasal verb because it's simply extra information tacked on to the word "crash". It explains what something collided with. The meaning of "crash" isn't changed.
"Get in/out" are phrasal verbs because the verb "to get" means "to obtain" or "to become". However, when joined to "in/out" suddenly the whole phrasal verb means "to enter/exit". The usual meaning of "get" is no longer important.
"To take off" (which has several meanings) works the same way. "To take" - well, I'm sure you know the meaning of the verb on its own. However, add "off" and suddenly the whole phrasal verb means either to ascend from the ground (a plane) or to remove (clothing) or to do an impression of someone.
In my opinion, "to set off" is a phrasal verb. "To set" means "to solidify" or "to put". However, "to set off" means to start the journey, or to complement. Again, the basic meaning of "to set" has nothing to do with the meaning of the phrasal verb.
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