when we will receive monthly bonus?
As before - in the first week of the new month.
Interest scheme airdrop after the swap NPSXFX tokens. And how many will keep the NPSX (NPSXFX) tokens and do not convert them into f(x)?
They distribute the monthly airdrop few hours ago after he inquire about this. What you are talking that is totally different than the actual question.
My first statement is true - tokens are distributed in the first week, not on a specific day of the month.
The second question was already for everyone and today I received a partial answer in this article
https://medium.com/pundix/2019-the-year-of-compliance-a04b4c249f4f.
Although the article uses the term "unlock" but in practice it means "airdrop", it has previously been used.