No planet in the universe can turn retrograde. A retrograde planet is just the result of an optical illusion.
All the planets turn around the Sun. Relative from our point of view on Earth, it appears sometimes that a planet will stop and go backwards called the retrograde motion, and then stop again and go forward called the direct motion.
During a retrograde period, it is not a good idea to push forward any practical venture. It is better to prepare for it rather than doing it and to move ahead later with the direct phase of Mercury.
Mercury goes Retrograde three times every year. As it slows down before the Retrograde period, we call it the Pre-Retrograde. Mercury starts losing power then and hence new ventures cannot do well in this period. Then there is the Post-Retrograde when Mercury picks up or gains speed but is still moving slowly enough to cause a slow progress in the projects undertaken. During the Mercury Retrograde period it is best advised not to venture into any new territory and to stay put. Actually Mercury keeps going around the Sun, always in the same direction and more or less at the same speed. Knowing the Mercury retrograde periods can help you to plan your ventures in advance so that they do not go off-track.
In 2019 Mercury Retrograde thrice. In March 2019 it goes retro in the sign of Pisces. In July 2019 it goes retro in the sign of Leo. In October 2019 it goes retro in Scorpio.
Mercury Retrograde! is an astrological app designed to help people determine if Mercury is Retrograde or Direct and when it is going to happen.It graphically shows where Mercury and Earth are in relation to each other and correct Zodiac houses. A color coded calendar counts down the days until future Retrograde/Direct events.