problem with brakes on Geo Metro 97

Hello!
I have Geo Metro sedan from 1997. Two weeks ago, breaks were changed. They worked fine till yesterday, when I went down form Yosemite NP. It seems that if it is downhill and if I push brakes a lot of time, in some moment they start to be very hard. I needed to push them very hard to stop. Also that happened if it is bad traffic and they are used a lot. In regular traffic they seem to work just fine. Did somebody experience this and know what is going on? Thanks a lot!

so, is the pedal harder to push, or does it require more pedal to use?

when was the last time you changed your brake fluid?

so, is the pedal harder to push, or does it require more pedal to use?

when was the last time you changed your brake fluid?

The pedal is harder to push. About brake fluid, I I did not change it, and I have this car half of year - I don't know about previous owner.

Thanks a lot!