'95 Firebird convertible, abs problem, brakes very slightly work in emergency at

I am in Michoacan Mexico, recentltly the brakes have all but stopped working.... I had a brake shop, 2 actually check for problems, they find nothing, calipers and drums and shoes all good.... when in emergency car bearly stops ...no abs lights are on, no warning lights are on, a/c seemed to stop at the same time.... shortly before this started I did hit, and run over a large rock in the middle iof the hiway here, but up on rack, there seems to be no visible damage or kinked or crushed lines etc.... any one there can help a poor Gringo, Gary Gato :banghead: