How to deal with the damage of precious calligraphy?

It doesn't matter if it turns yellow a little. Ancient calligraphy works are all like this, showing the traces of the times. "There are several places in the middle where the ink is very thick and rotten." Is this rotten by creases or by cockroaches and bugs? The former need not worry, but the latter is more troublesome.

Two suggestions: 1. Find a mounting shop. If it was originally installed, it should be repaired. If it is not mounted, it should be mounted. None of the problems you mentioned are the problems of the makers.

2. Don't mount it or repair it. Flatten it, dry it in the shade (without sunlight or external heating), dry it thoroughly and store it in a sealed container (tin can or special container for painting and calligraphy). After ten years, its value will increase several times.