According to the Wall Street Journal (https://tinyurl.com/2p8w9kcw) :
NATO says that up to 40,000 Russian troops have been killed, wounded, taken prisoner or are missing in Ukraine, said a senior military official from the alliance.
The North Atlantic Treaty Organization calculates the figure based on information provided by Ukrainian authorities and information obtained from Russia – both officially and unintentionally, the official said.
NATO estimates that between 7,000 and 15,000 Russian soldiers have been killed since the invasion began on Feb. 24. Using statistical averages from past conflicts that for every casualty roughly three soldiers are wounded, NATO analysts reach their total figure.
Russia began its invasion with roughly 190,000 troops. It has since brought in additional troops from Chechnya, Syria and other locations.
As I said, I am way ahead of the news cycle and have heard confirmed reports that the Russian army has been beaten around Kyiv. Makariv, Bucha, Irpin, Dmyrivka communities have been retaken by the Ukrainian military, but those communities remain under constant enemy fire. I have heard that the Russians in the East of Kyiv have also been beaten. That means the war shifts to the Eastern part of Ukraine where the Azov Battalion is defending Mariupol. Source: https://rubryka.com/en/2022/03/23/zsu-vzyaly-v-kiltse-irpin-buchu-ta-gostomel/
So, why was Russia given the advantage and Ukraine going to get defeated according to Western Intelligence sources? Ukraine's social media is filled with disappointment at the quality of Western military analysis, in particular, over-estimating the ability of the Russian army. Most people explain this as Western experts reading Russian sources and believed them. On the other hand, Ukrainians had direct practical knowledge, but they were pretty much ignored by the Western Agencies. Now, The Ukrainian military and defence studies community also produced a lot of literature in the last 8 years will probably be read, but it's too late now.
I have to admit that I though the Russian military would have done slightly better, but I knew the Ukrainians would put up incredibly strong resistance. I also didn't expect the amount of unification that the Russian invasion and subsequent war would cause.