4
This is just my opinion, I don't see Mars as a malefic and it is positive half the time.

One possible interpretation of transiting retrograde Mercury conjunct natal Mars could be a musician or artist going over their piece of work.

A lot will depend on what Mars aspects in the natal chart, and also what the longer term transits and Solar Arcs are doing.

Often the effects of retrograde Mercury are too subtle to notice.

5
Mercury rules things like communications, contracts, speaking/listening, documents, travel, business.

Delays and loopholes are more likely during Mercury retrograde.
You are being asked to re-organize, re-think, re-do, re-sign, re-send documents, re-visit, re-open, all sort of things you thought were done and finished.
When Retrograde over Mars, you are being asked to re-organize your energies to become more energetic, more efficient and have more free-time. There is a need to start something new in your life or get involved in a new project or go on an adventure
At the same time, the Retrograde period may find you head over heels as in a somersault where frustration can arise from things not moving quickly enough. Be careful if you travel.
Take time to reflect at what you are doing and why you are doing it.
On the plus side, this is an excellent transit to clean up your house :D

Ouranos
Blessings!