Hello.
Hope all is well with you.
I have not heard any samples of the audio, but in my experience, most audio issues are fixable.
I use izotope RX7, Sonnox Restoration Suite and other software tools for audio fixing.
My editing and judgement are also worth noting.
My guess is the audio is boomy or muffled with plenty of rumble and unsatisfactory quality.
On a job like this, the correct steps need to be taken in the right order to maintain and keep what you want kept, then a bit of mixing and enhancement.
I can have the work done pretty quickly and cheap too.
Any complaints on the price, let me know, we can talk about that.