At Pyanodon the Railways are reseached first in "Railway 1" and normal Railway Research is disabled, so i can't research and build the bridges

Same issue for me. What would the fix be? Gate bbr behind Railway 1, or behind some later tech?

so, you should only add this to to data-updates.lua

-- technology
local techname = "railway"
if mods["pypostprocessing"] then
    techname = "railway-mk01"
end
table.insert(data.raw["technology"][techname].effects, {type = "unlock-recipe", recipe = "bbr-rail-wood"})
table.insert(data.raw["technology"][techname].effects, {type = "unlock-recipe", recipe = "bbr-rail-iron"})
table.insert(data.raw["technology"][techname].effects, {type = "unlock-recipe", recipe = "bbr-rail-brick"})