I have an issue where track is silenced at multiple places, the track is long so i can’t really check whole track and do copy paste, i need to fill those places with sound from second track, i did normalization on first track but still didn’t do it on second one, that’s why it is quieter than first one, i just need to extract audio from second track only on those places where audio is missing on the first track, i need to do that because first track has Serbian language and second one is in French language. Do you maybe know how can i do that, or if i can’t in audacity, which program has that option?
If it were me, I would just let the tracks mix when exporting. The quiet track will get drowned out by the louder track everywhere except when the louder track is silent.
You can look into AutoDucking, but it really only works smooth when you manually adjust it yourself, which you said you don’t want to do on a long audio.
Ill check this AutoDucking section it seems that you answered my question, ill check it and mark this solved if it works!
I tried it but auto duck amount cannot be below -24, it would be nice if they made it go -100 
Ill leave this open, maybe someone has better solution with some third party plugins or something
This guy resolved fully my issue: