Need help with copyright

As you already know, I'm working with the cycle named "the Chronicles of Guardian". Actual plot is original, but there is one bigl thing, that instill some uncertainty - one of the universes, used in the first book is Freelancer.

So, what I have now:

1. Freelancer plot is not main and not even background. Its only the part, one of the stops on the further the plot.
2. FL universe is actually a large decoration to some scenes
3. The whole plot of the "CG: Final Initiation" depends on it, becouse it's a place, where several key events happens.

What about copyrights? Are there any "pitfalls" of which I should know about? (Russian copyrights have some differeces)

Becouse the first book is ready and finally edited. I can send it to the publisher right now.

Thanks in advance.

That's why i'm asking. Currently, the book is only on Russian, but can be translated.

Well, it's FL universe. Of course, there will be a plot of FL. One of the anomalies occurs, through which lot of people jccasionally come here from other worlds, in exactly for weeks before the Freeport explosion. Also, the Solar System destruction (by supernova weapon, as you also know from BC prehistory) is one of the keys to the anomalies nature. Yes, the Vanilla events is still a background. But a strong background to accompaniment of other events which take place.

P.S. Here the planned books scheme (translated, some of them are consumed by others):

No problem. Just give me your contacs to send a text file. i will not translate it by myself (I believe no one needs to explain why), but will constantly observe the process for shure. The more such readers, the better probability of a good translation.

But in the beginning it is better to dot the i in respect of international copyright law. Whatever the outcome - in Russia is nothing prevents the spread of the book. Especially because I rely mostly on the free electronic distribution than on efforts of the publishers.

I meant just in case, but ok