Is Supergirl more powerful than Superman?

IS Supergirl more powerful/or stronger than Superman?

No, the very idea goes counter to the standards of the universe.
Although there was a time in DC Comics that Supergirl appeared stronger than Superman, it is only on the CW TV shows, where this false idea rules.

Men are naturally stronger than women. That's a fact when you look at any world records, regarding strength, power or speed.
Kryptonians would be no different.

Also, Superman has spent much more time on Earth, absorbing more yellow sun radiation than Supergirl.

The CW show, "Supergirl" simply goes out of its way to demean Superman and make him less powerful.
This was very evident in the network's December of 2018 crossover event. Superman was all but worthless in that series. All he did was serve as a punching bag and he added nothing to the plot.

(And, my prediction is that if any hero dies in the sequel to that CW crossover in December of 2019, "Crisis on Infinite Earths," it will Superman, not Supergirl who perishes.... as it was Supergirl who died in the original comic book series of "Infinite Earths.")