LOL Saieen baba ki poetry is absolutely 
Re: The mother tongue!
You can't express yourself as well as you can in your mother tongue, no matter what you do.
Now after few months, marriage is all about communication. And I have seen most issues start with miscommunication and misunderstanding.
Ye culture culture kya hai, ye culture culture! 
It is a group of beliefs, norms, and lifestyle of a large group of people. It develops from a number of factors including religion. Many aspects of culture can and will not be in line with any one religion and that could primarily be due to mingling of people from more than one religion - people with different religious beliefs who settle down in one part of the world develop a culture over time.
That boring mumba jumba aside, you cant run and hide from your culture. It exists, accept it and live with it. Dont follow what doesnt seem right, but closing your eyes to it doesnt make it disappear. And it is advisable to choose a partner that is a part of the same culture - ideally this way there will be lesser differences and easy adaptability.
Re: The mother tongue!
Mother tongue does not matter,but tongue matters.