Inferno – “A fitting image for you” [Campaign 5, Mission 2]

Hi everyone. I've loved and respected the series of games for a long time. I'm currently playing Heroes 6 for the second time (I didn't finish it the first time because of bugs, and the first mission of the Demon Campaign annoyed me). However, the current situation has forced me to register because it's impossible to continue playing. So, as I understand it, this mission is impossible to complete? I can't see any other explanation. Basically, at the beginning of the first week, I captured a Castle and slowly developed. At the beginning of the second week, I ventured into enemy territory because there were no decent resources for development, and with great difficulty, losing almost all my dogs, I captured a town with Rosalind. At the end of the second week, a second Light Alliance mage hero arrives. I don't know how, but I somehow managed to hold on. Only one Lilim and 8 Fanatics remained alive. Otherwise, there was no way; the level 12 mage was simply mowing down my troops with his spells, and I couldn't do anything about it. What else could I do? Sit in the first town without resources and wait for him to attack the town? That would also be a disaster, just a week later. So, at the beginning of the third week, a Necromancer hero appears with an army posing a deadly threat. And now I feel that the end is near because, with my army, considering the previous losses, I can't resist. And is this normal? I've been playing Heroes for 8 years, and I've completed all the previous missions in Heroes 6, but I haven't seen this problem before. In Heroes 3, if you rush, you could easily capture several enemy towns at the beginning, even on a difficult level in the Campaigns (although I don't like doing that). Because he couldn't quickly gather troops, which is logical. But here? Is it impossible to do that? Are there huge armies with mega-super-duper level 12 heroes right from the start, and I can't do anything about them? Well, thank you very much. In general, maybe someone can suggest what to do here. I don't see any prospects in this mission, even if I try my best. Sorry for the long text, but this really annoyed me. I wanted to relax after work, but this isn't relaxing; it's just a constant source of stress