Both sides are having a bad time there.

Russia has been trying to take that city for like 6months and suffered a ridiculous number of casualties trying to do so. At the same time Ukraine has lost a lot to defend it.

Russia really wants to capture the city as some symbolic win, so they're just throwing everything at it. It means they suffer a lot of losses, but also slowly make progress.

Russia should have given up on that city ages ago and tried an offensive somewhere else.