M.P.
My granddaughter is now 20 months and just recently begun to say more words than just baba, mama that can be understood. She only recently said Dada and is working on Gama. Mostly she calls me mama. I think that your boy is probably doing fine but you could check with his pediatrician to get his opinion.
I'm guessing that you also talk with him in your native language. I've read that toddlers who are learning two languages talk later than those with just one language. If you're not talking with him in your native language I urge you to do so. It's really helpful for us to learn two languages and we learn best really young.