Walkthrough tips, Discussion of Campaigns [Heroes 5]

Guys, please help me. I'm new to this game; I only bought the coveted disc yesterday and have never played it before. I completed the first mission easily, but in the second one, called "Rebellion," where you are given a week to conquer a city, that week ends quickly, and I don't even have time to find the city! I hope you can help me and give me some advice!!! I will be extremely grateful!!!

Please advise! In the Warlock campaign, I think I've dug up everything in the expansion missions, but there's no effect! Where should I dig? (If possible, explain in detail as if for someone not very bright).