Cursed Lands

I personally upgraded the sword to level 2 on the Hippogryph so far, level 1 Fire magic, melee 40, dexterity 10, astral magic, magic of feelings 20.

This is an absolutely ruined character; he will no longer be able to become a beast. I hope you noticed that when upgrading each skill, the cost of all the others in terms of experience approximately doubles, i.e., each skill needs to be upgraded to the end (that's how the prices are distributed there), and then move on to the next one. It's useless to upgrade the sword; it's weak in the game, as is Fire magic. If you want to level up a mage, reread the previous posts. If it will be a warrior, then max out Backstab, and then move on to Spear. You can also take a look at Action, as well as Strength and Load. Magic is leveled up for specific spells and is cheap.

And what does Ayri have to do with it? What does she do? I personally strip all the helpers and leave them... and I level up with just one Castle.

At a certain point in the game, Ayri gives +10 skill in Magic of Feelings as part of a quest, along with the necessary experience for it. When completing a genocide-style playthrough, your feelings increase from 70 to 80, which is quite a lot of experience. By Hippogryph standards, it's VERY a lot.

I can't kill experienced skeletons in the Dead City.

This is a consequence of your poor character build. There are many possible builds in the game that will allow you to easily complete almost everything without any difficulty, but yours is far from that. I advise you to restart and develop your character properly.

And I don't understand how to kill dragons at all.

This isn't your first playthrough, so don't worry about it. This requires not only a manual but also skill, which comes with experience.

And how do I complete this stupid quest with the Cyclops? The cyclops keeps coming and killing me.

You buy a bow. You slowly crawl around (so as not to be noticed) and kill the innocent little piggies one by one. When you kill them all, the cyclops will hang around for a bit and then leave on his own. Read the quest descriptions carefully.

And why can't I insert as many runes as I want into a spell?

All spell bases and runes have a DIFFICULTY parameter. When creating the spell itself, the complexity parameters of the components are summed up and cannot be greater than the skill in the corresponding magic + bonus from upgrading the skill in magic (+0/5/10/15) + intelligence value - 25. That is, if you didn't level up Intelligence, then the last term becomes zero. I repeat, but read the descriptions in the game of everything you can. The hints, descriptions, and the help system in Might and Magic are simply excellent.