The article (in German) claims that Russia dumping all the government bonds it is currently holding would be detrimental to the US as it would raise America's cost of borrowing. Quite frankly, this is a highly dubious claim and it makes me wonder whether the person working on that article did even bother to check whether the numbers actually add up.
According to Wikipedia, the total outstanding US national debt is about 21 trillion USD, which is in excess of 100% of GDP. Total Russian foreign currency reserves are a little less than 460 billion USD, and less than half of them are dollar denominated assets (see Reuters). Even if we assume that all of the dollar denominated assets are US government bonds, which seems somewhat unlikely, then Russia is only holding about 220 billion USD of American debt, which would be just about 1% of the total.
Even if Russia were to dump all of her dollar denominated securities within a relatively short time period, I doubt that this would have any meaningful impact on financial markets and the US interest rates on government securities. The best and safest bet is that other market participants would simply swallow the additional debt and that US yields would not move very much. How do I know this? Well, the Republicans just passed a trillion dollar tax cut, which was basically a handout to the super-rich and American corporations, which also blew a huge hole in the fiscal budget. As a result, the US fiscal deficit increased from about 580 billion USD in 2016 under Obama to about 830 billion USD under Trump in 2018, and is likely to approach about 1 trillion USD for the years 2019 and 2020. Because the tax cut will only have modest supply side benefits and the any substantial demand side boost will be offset by the Federal Reserve, the claim that the tax cut would pay for itself was always a bad joke. Trump and the once fiscally conservative Republican Party just managed to engineer one of the largest increases in the federal debt under peace time while being in a regime where the economy is rapidly approaching full employment. So what happened to US interest rates over the last couple of years as both the deficit and the US debt are surging? Well, the chart below shows that US interest rates barely moved upwards over the last couple of years. The claim that Russia dumping all its dollar reserves will substantially alter the path of US interest rates does not stand up to scrutiny. And even if there was some substantial movement in the very short-run, the Fed could always act as a buyer of last resort and swallow up some of the US government bonds that would be dumped on the market.
PS: Please don't read my post as saying that the increase in the US debt as a result of the tax cut does not matter. While it doesn't really affect US borrowing costs at the moment, it is still a bad idea to increase public debt by such a degree and with such waste because it reduces fiscal space when the next recession hits the US economy.
PPS: The claim that Republicans are fiscally conservative is also one of the biggest jokes ever. The only president in recent decades who managed to reduce the debt to GDP ratio is Clinton. Under Obama, it basically was all about sabotaging the presidency of a black president. The entire Tea Party movie was basically racist, the precursor to Trump.