In comparison to dogs, no, gerbils are not super-intelligent. However, in rodent terms they are clever little critters.
Gerbils are inquisitive - always a sign of a bright mind in any animal - and dig complex tunnel systems with lots of different entrances and exits. They also have lifelong social interaction with other members of their species, which takes a modicum of intelligence too.
Mongolian gerbils set aside different areas of the tunnels for different activities. Some bits are used for sleeping, others for eating, and some for toilet purposes, while other parts of the maze act as intersections and links to other areas. It's clever stuff.
Gerbils spend much of their time burrowing, and need plenty of suitable material in their enclosures
For all that, you will not be able to go beyond hand-taming a gerbil. That's as far as training goes. If you want the cleverest of the pet rodents, it has to be a rat every time. Rats can be trained to a certain extent, and will interact with you in an intelligent and affectionate way that is simply beyond the abilities or inclination of the other rodents.