Print invent a conlang that works with the existing manuscript to give
something intelligible.

Pick a sentence.
Decide what you want it to mean.
Work out the English gloss.
Start building up the dictionary.
Move on to the next sentence.
Rinse and repeat.

You might want to start by working out a usable division of the characters
into vowels VS consonants.
Then collect word frequency statistics to know which words you want to make
into nouns, verbs, prepositions, particles, etc.

Even just "translating" one page into a conlang would be a real challenge,
but just think how famous you could become for "solving" the manuscript!