At the moment the Ukrainians substantially outnumber the Russians, or at least those Russians deployable in Ukraine.
Until such a time as the Russians are willing to treat this as a total war and mobilize all their reservists, that will not change.
That may or may not allow the Ukrainians to go on the offensive and reclaim their lost territories. Western military aid helps to that end, also the relative obsolescence of Russian materiel and the so far poor standard of operational ability the Russians have displayed.
At the moment the war is quite even in terms of balance of forces, notwithstanding the Russian Air Force, which is also performing poorly, given its (on paper) overwhelming numbers. Its up to the Russians to decide whether they are sufficiently politically committed to go to the next level.
Russia committed the majority of its deployable forces in the first wave the rest in the second wave.
It has no reserves.
It has been trying to get guys who retired in 2012 to come back and trying to get mercenaries from central Africa and Syria.
Russian military comprises largely of forces to keep internal dissension down. Plus they have a large border to defend.
The Russians have already treated this as total war, with their economy destroyed to focus on the invasion.
The Russian air force, navy, tanks etc look good on paper but the vast majority of craft are mothballed. The remainder are poorly maintained if at all