How to create a foreign language font?

I have tried to create a new font in a foreign language. I have the vectorized the shapes of my letters and I was able to export it in .ttf. Then, I can access to all the regular Latin characters (a,b,c, ect) by selecting "Latin Basic" but not special characters (like Γ,Σ,Ψ,Ω,Π, ect) by selecting "Greek". It says that it doesn't support symbol fonts even though I have check the symbol font box. I don’t know what else to do. Is there a solution for that kind of problem? Thanks,