This stuff is so far outside my areas of expertise that I don't even know how to begin to comment on them, to be absolutely frank. But they are certainly important, and I strongly recommend reading both of them in their entirety.
1. Franklin Foer at Slate: "Was a Trump Server Communicating with Russia?"
2. David Corn at Mother Jones: "A Veteran Spy Has Given the FBI Information Alleging a Russian Operation to Cultivate Donald Trump."
What I can say is this: Donald Trump is unfit to be President of the United States. His connections to Russia, whatever they are, is just another on the laundry list of disqualifiers.