After visiting a dentist who tried to smooth out one of the filling he did poorly between my teeth, i noticed my gum has gone up causing a black triangle space between the teeth. could this be his fault? the filling is still not smooth?

The interdental papilla will usually recede if there is underlying bone loss, something that only your dentist can tell you. Depending on the location and size of the carious lesion the restoration may not have fully filled the embrasure. So hard to determine without a visualization.

When fillings or laboritory prepared restorations a made the plan is always to have a smooth margin continuous with the tooth against which the gum can grow back if the area is kept clean, the spacing is normal and there has not been bone loss. Having an overhanging restoration is a plaque trap and it should be removed, sometimes smoothing can be achieved, but it is best to restart.