"Geography lesson is good" is not proper English. "The geography lesson is good," "Geography is good," "The subject of geography is good"... all those would be fine.
I think the English needs to be corrected with some degree of consistency. It is either the subject (Geography, History, Physics, Science etc.) or Geography subject, Science subject, etc. Also why not be consistent with languages - Kiswahili is clearly Swahili language. Note that it is OK to say "I am studying English language" as opposed to studying English literature, or English history. I study the history of the Swahili people - Ninajifunza historia ya watu wa Waswahili.