you have to add a "e" before "o" to have the sound as "jo/in' otherwise you'll have a sound as "go" je mange tu manges il/elle/on mange nous mangeons vous mangez ils/elles mangent
same when you'll have to conjugate at the "imparfait" je mangeais tu mangeais il mangeait nous mangions vous mangiez ils mangeaient
so before the vowels "a" and "o" , you have to add an "e" to get the sound "je" as "join'...otherwise you get an improper sound as "go"
Not sure my explanations are very understandable, but I tried !!!
