I'm Nicolás Ocampo, I'm a composer, music and audio producer (editing, mixing and mastering), and academic copyist received at the Facultas de Bellas Artes, Universidad Nacional de La Plata, Argentina.
What kind of game is it and what is it about? since that depends on the instrumentation used and the character of the music.
I also need to know how much music time you need, and how many movements or sections.
The time it will take to compose the work will depend on all this. eg: if you opt for original contemporary music, the time will be longer, but the music will be more interesting, but if you opt for orchestrated melodies the time will be less, but it will be more "conventional" music.