What is the best way to learn Latin quickly?

Answer 1

Probably take an intensive summer Latin course, or two. I find that learning new languages in that kind of environment is the most helpful/productive way to do so.

They typically run five days a week, five hours per day for about one-and-a-half months, with roughly three hours of homework per night. It's a full time commitment but worth it.

After doing that, you'll be prepared to read intermediate texts with some assistance, e.g. a commentary and dictionary.

I don't think you can really learn Latin "quickly." To become professionally fluent, you're looking at 10+ years.