The Ukies can’t halt anything. If the Russian advance stopped it was because they decided to pause…. regroup, resupply, rotate out troops- the Ukies do not have that luxury.
It would be unusual to rotate and regroup troops after only a few days of action.
They have halted the Russians for over two years, minor and insignificant advances notwithstanding. I do not understand this Bagdad Bob denial of real Ukrainian achievements. It does not lend any credibility to your position.
Stopped mostly from their massive casualties - all told Russia has lost over 9000 troops in the past 3 weeks, which would equate to around 3000 dead.