When a dasha is running, the planet running the dasha has more power over your life. I've heard it can take a few years between dashas to really shed the previous dashas energies, especially if you are switching between longer dashas.
Saturn dashas are hard generally, even if your Saturn is a benefic. Saturn is the planet of hard-work, maturity and responsibility, so his dashas revolve around these themes. He is also the planet of delays and restriction.
For Gemini ascendants, Saturn rules the 8th and 9th house. 8th house is the most malefic house, because it is the house of unforeseeable changes. Some 8th house themes are: death, inheritance, major transformations, accidents, surgery, secrets, what is "hidden" - just to name a few. Saturn also rules your 9th house, so there were themes revolving around the father, higher education, religion, long-distance travels, gurus, dharma etc. There is a connection between the 8th and 9th house, so sudden changes were susceptible to 9th house matters.
Mercury is the planet of communication, the skin, electronics, computers etc. Mercury is like the prince in a kingdom. Saturn is the old man. Mercury dashas are all about experimentation. Mercury in your chart rules much better houses - the 1st and 4th - and it is placed in your ascendant in it's own sign. 4th house matters will come directly to you; property, the mother, land, vehicles, houses etc. The spouses career will also become very important. Your Mercury is in the nakshatra of Aardra. Aardra is all about renovating old things.