Is Russia in a deep economic crisis? Premise: I see that the site is for professional and academic economicists, and I'm neither. However,  since I've been participating to other SE sites for some time now, I consider SE a trusted source, and reading here I think my question is on-topic, thus I'll take my chance and ask.

I was talking about Russia at work, and a coworker started saying that Russia is, and has been for a lot of time, in a deep economic crisis, nearly on the verge of bankrupcy. This guy is used to pretending he knows all about everything, thus I don't trust him. But, come to think of it, I noticed that I know very little about Russian economy: I don't know if it has a large national debt, who's the owner of that debt (Russians or other states?), whether it has a positive or negative trade export, etc.

On one hand, I guess Russian economy must have taken a blow from the failing oil prices, because lower prices => less profits for exporters like Russia (right?) and also because cheaper oil => less market for gas, which Russia also exports. However, shouldn't this be compensated by higher oil exports because of the lower price? I'm getting a bit confused here. Also, sanctions against Russia must take a toll on its economy. 

On the other hand, Russia is considered a big international power. It has a lot of natural resources, and one of the strongest armies in the world. It seems weird to me that a nation "on the verge of bankrupcy" could mantain such a military power. Is my coworker really mistaking Russia for old Soviet Union? Or is he right, and Russia is actually down to its feet in a dramatic crisis?
The Russian economy has been in an recession since 2014, when oil prices plumited. The Russian debt to GDP ratio is still very low though:  below 20%, compared to over a 100 for the United States. This is because Russia had a huge stash of cash before the recession, which has shrunk from over 91 billion in 2014 to 32 billion. If this trend continues at some point they will have to start borrowing money to pay for expenses. But I don't see them going bankrupt anytime soon, because their debt to GDP ratio is so low so investors will lend them money against low interest rates.