Good evening,
I am an audio engineer with years of professional and academic experience in editing, mixing and mastering audio on the best DAWs and on analog.
It is almost impossible to remove echo from a mixed audio, but if you have all the mic recordings, and the echo that we hear is the spills from the other, then I can fix your problem with a precise work of editing. After that I will take away all the possible noise and mix the vocals together (and finally master it).
I hope you could be interested in my proposal and I hope to further discuss my chance to work for you.
Best regards.
Mattia Battegazzore