What sort of activities could humans do on Mercury if they were able to survive on the planet?

First of all set up an energy sources, nuclear power is most possible way to get the electricity, then set up an internet line, open FA on Mercury!!!

When I was a lad scientists believed that tidal forces caused the same side of mercury to always face the Sun; just as the same side of the moon always faces the earth due to tidal forces. If this were true than the side facing the sun would bake at about 750F while the opposite side shielded from the Sun’s rays would be only slightly above absolute zero. It was thought there might be a habitable zone at the transition

However, mercury’s day is in fact longer than its year. Since the Mercury night is 59 earth days it may be possible for people to spend a period of time on the dark side. If they were able to dig in deeply enough the base may even be suitably insulated to survive the 59 earth day period of the mercury day.

Not much, too cold or too hot to build anything that could return useful material to earth. Best idea is to attach rockets to Mercury and move it farther away from the sun so we could mine it.

They could stand the high temperatures, explore new unknown territories and make new landmarks. Then, we could proceed on to inhabit other planets.