The content related to the handwritten newspaper about speaking Mandarin in English can be expressed as: \The content about the handwritten newspaper on speaking Putonghua\
Or
\The relevant content of the handwritten newspaper concerning speaking Mandarin\Another possible expression could be
\The content related to the handwritten newspaper of speaking Mandarin\ These expressions can be used to describe the topic you mentioned. The choice of which one to use depends on the specific context and your personal preference.
