Does it Help or Hurt SEO if You Change the Name of Blog Post?

When I first started, I had no idea what I was doing (I still don't have a clue, but I'm getting better), so I wrote a bunch of blog posts that need improvement and they still aren't ranking. Some of the titles/URLs are super long and I am guessing (tell me if I am wrong?) that shorter titles are better.

As an example.... If I posted an article called 100 of the best blenders to make yummy shakes (not a real title), can I change it to 'best blenders"? Will that help SEO? Or hurt it?

Can I even do that??