"Raj gives me mangoes."
Translation:राज मुझे आम देता है।
आम is masculine and all masculine words that do not end with अ (a) take the same form in plural as singular. Thus आम can be both singular and plural, so in this case it actually is plural
Why is it मुझे if there is no postposition/ the sentence is not oblique? Why isn’t it “राज मैं आम देता है”?
RanzoG has explained your question precisely, but to add to it you can just think of 'मुझे' as 'me' and 'मैं' as 'I'.
Like saying 'Raj gives I mangoes' would be wrong in English, the same applies to Hindi
/mujhe/ is the contracted form of /mujh ko/ (like, it is = it's)
"Raj to-me mangoes gives"
आम is masculine and all masculine words that do not end with अ (a) take the same form in plural as singular. आम can therefore both mean mango (in singular) and mangoes (in plural). In this case it actually is plural