Using progressions will help you to play by ear better and help you to play in all keys faster. It's just like scales, except now you are dealing with chords.
A progression is just 2 or more chords played behind each other with each chord moving or progressing to the next chord. Once you get good at practicing them and hearing how they sound, you'll start to anticipate what chord will come next. Thus, strengthening your ear and your ability to figure out songs quickly. It will even help you to play songs you've never heard of or practiced before just by recognizing a pattern.
There are many topics on progressions, so you should check them out and start learning. If you need help along the way, don't be afraid to pm me. I will do my best to assist you on your musical journey.
