Page repair ideas

If there is material added to the surface of the page, I would try the following.

With a cotton swab I would try to remove as much of the material as possible - using some solvents, obviously. The most obvious are water and acetone. Test the process on the white space between the lines. If it works, try above some letters. Be prepared (especially in the case of acetone) that it will dissolve the letters - which you do not want.

At the end, you might want to use a black fine-tipped pen(cil) to redraw the letters - to bring the page as close to the original look as possible.

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If material is missing, just use the last step above - the one with the pencil.

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If you are more technically inclined, you can try to re-write the same test in your preferred text editor - using the same fonts, size, letters' position etc. Print the text - you may need to do several steps, until you get it right. When it is right, your printed paper should look like it was cut from the book.

Once satisfied with the quality of the copy, just cut / crop the printed paper and glue the paper fragments to the book page - fitting / aligning the fragment "perfectly" with the original text.

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A glued glass fell on it and I removed it without much care.

If you know the exact glue, then you might be able to find the right solvent for the cured glue - and use it as explained above.