Hi! I've listened and watched (the audio spectrum in my editing software) carefully the mp3 sample file.
At first listening, I have to say that the interviews needs to be edited one by one, because each of these has different main audio problems.
For example in the 1st audio the volume of the interviewer is different from the interviewed, and needs to be ''leveled''. Instead in the 2nd the main problem is the wind sound, and needs some EQ.
At the last interview the sound is on the ''right'', I will provide to bring it to the ''center''.
I will work meticulously on each interview and I will provide 9 different WAV audio files. I think it's even better and pratical for you in the moment you will put the video on. Otherwise I will edit them one by one and I will put them togheter again.
Once I have done the big part of the work, i.e. fixing the main problems, I will move on the part relating the improvement of the sound to be more nice and pleasant to hear. At the end, the work will sound clear and good.
Noises like the one at 5:49 can't be edited or restored, because the noise is (a lot) more louder than the voice.
I will use tools like: de-essers, de-noisers, compressors, eq and everything I need to make a great sound.
Obviously I prefer work with a WAV file and if you have made changes (e.g. on the equalization, volume) please let me know.
I hope to help you with this interviews so we will have all the time necessary to talk to improve the sound.
Best Regards, Francesco