I'm no military expert, so take everything I write with that in mind. I'm just really good at analysis, math and logic, and apply that to what I read. Over the decades I've also (with the great help of my wife!) developed a pretty good bullshit detector.
That detector is why I only look at western maps and almost exclusively western sources. I don't have the cultural background to try to figure out how much Russia is lying (a lot I'd guess!). I do much better at sniffing out the heaping piles of bullshit the west is spewing.
With that background...
There is no way Russia has lost 50% of its forces and is still functioning as a cohesive army, or 80% of its tanks. What I've read says anything above 25% and it is togh for a unit to function.
When I look at liveuamap I see Russia advancing every day in the Donbas. Right now there are about 70 "Russian attack icons" stretching from Kharkov to Mykolaiv - a roughly 1200 km front. Russia could not hold, let alone advance, along a 1200 km front with 50% losses. That doesn't include the remaining Russian forces fixing Ukrainian forces around Kyiv, etc.. 50%+ loss and the activity on the ground is just not possible.
At the begining of the war I saw western pictures showing thousands of reserve tanks (old, but functional) that Russia has available. A quick search of western sources from April says Russia had 2800 tanks ready, with another 10,000 in storage. They ain't running out of tanks anytime soon. Those numbers don't include 13,000 other ready armored vehicles with another 8,500 in reserve. Of course, what we've seen of Russia's vehicle maintenance might mean they'll have another 40km breakdown like outside Kyiv...
BTGs are not "the active Russian Army." They are battle-ready groups that Russia can send to to "hot spots." That is how Putin could lie about this not being a war because the main active Russian army is still stationed wherever they were before the war... I mean "special military action" (wink-wink).
This above with my previous comment: Russian salients are about to close around Lysychansk. Another closing in on Sloviansk. If Russia takes those two cities they both get major psychological victories and shorten their front lines. They are then in great positions to take Bakhmut and/or Kramatorsk.
Russia is advancing much faster in the last days. As I noted, Russia has destroyed most of "The Donbas Line" allowing much faster advances in that area, and getting more Ukrainians to surrender.
Back to bullshit detection. The US state department lies, spins and may even believe its own bullshit. The Pentagon is more honest. It is not a coincidence that Lloyd Austin called his Russian counterpart for the first time in two months last week... and asked for a cease fire. It is not a coincidence that Zelenskyy two days ago finally started talking again about negotiation.
The Pentagon knew that Afghanistan's army would fold like a cheap lawn chair when we pulled out. They just spun it as a surprise to make Biden look bad for finally getting us out of a war. They also know that Ukraine is on the edge of some serious battle defeats that may turn public opinion away from continuing to throw good money after bad in destroying Ukraine for the bottom line of the US MIC.
The WaPo published the most realistic article about the situation in the Donbas 1-2 days ago in an effort (IMO) to "foam the runway" for the impending defeats there.
As I said, we'll know in a few weeks if I'm right.