11 month old not talking

Hi all,
We have a 11 month baby boy who is making lots of sounds- ma ma, da da, ba ba here and there but not regularly.
We are worried- what shall we do. We are trying to talk to him as much as we can. I am a stay at home mom and he is wfh.
My husband and I speak mainly in english and language of the place we grew up in .
Sometimes in our native language too , which I am not extremely good at- he is.
At times we also use a language we both picked up from friends- he is good at it , but I can manage.
This is pretty rare but we are planning to use as a code language to indicate chocolate for instance.

The dilemma now is how do we teach baby to talk- wondering if he is not talking because of all three languages thrown together.
Grandparents went back recently and would talk to him in our native language.
They videocall regularly and would visit again next year.

I have read little bit about OPOL method but what language shall we use when my husband and I talk? third language or one of the two which we use?

Could anyone tell me more about 5 books per week method? My husband and I cannot read or write our native language. We currently read books in English.

Please help.

Thanks.