It’s been estimated 400,000 Ukrainians have completed National service in the Eastern conflict since 2014. Add that to the regular army of 200,000, they have a lot of decent soldiers.
In 2014, the Ukrainian army was woeful, poorly equipped and just capitulated in Crimea/Donbask. Since then the West has been arming/training them. They have more Western anti tank portable weapons than Russia has tanks. Any old basic RPG will take out a truck/armoured personnel carrier.
Add in the fact that the Russians can’t leave the roads (Rapistuta mud season) and the roads are blocked with destroyed/broken down/out of fuel vehicles, the Russians around Kiev are in a world of s@@t!