All right... I think I can see where the issues are here, let's see if I can point you in the right direction. A common problem comic artists face is that we're encouraged to get good at drawing, but there aren't a lot of resources teaching us about structuring narrative.
It is true that a slow start is a disadvantage on Tapas (ugh, don't I know it...), but it's not an insurmountable obstacle. The issue I'm seeing is that the story has a lot of stuff happening, often with complex conversations, lots of characters being introduced and a high panel count...but without it being obvious what it's building towards, leading to a lack of rising action or hanging intrigue to really keep an audience excited to find out what's going to happen.
We open with this expansive shot of a city, and then we meet this old man... and it's all sinister... but then these two kids appear out of nowhere, and I'm like "okay is he imagining them?" and then their mum turns up, so I'm like "wait, are they actually just real children who just appeared in the creepy tree chamber?" But before I can get my bearings on this complex scenario that's been set up, he's telling the story of the actual story of the comic....But the problem is, he never tells the kids/the audience why he's telling this story, or what it's the story of. This is a problem because it's like asking your readers to get on a bus without telling them where the bus is going. If you tell somebody "This bus is going to Disneyland" it's like "Oh hell yeah! Okay! I'll get on this bus!". Even if some of the bus journey won't be super-exciting, knowing the bus is going somewhere exciting can keep the passengers focused, and happy to enjoy the more chill parts of the journey because they know it's setup that will pay off with excitement and fun later, but it's a lot harder to convince people to get onboard if you don't hint that the destination is going to be somewhere cool or interesting.
Generally, in works where there's a framing device of a character telling the story, like say, The Taming of the Shrew, Frankenstein, Wuthering Heights, they usually introduce why they're telling the story. So The Taming of the Shrew's framing device is that the tale is being told to a man who feels like his wife bosses him around as an example of how to control his wife (that play is kind of problematic, I'm just using it as an example of using a framing device), in Frankenstein, Victor Frankenstein is found in the arctic by a bunch of sailors and tells his story to explain what he's doing up there, aiming to teach them a lesson about the dangers of hubris, and the captain writes it down to send as letters to his sister. They set up an interesting outcome in terms of "What's the answer to this problem?" or "How did the character get into this wacky situation?"
So if you're going to start your story with a framing device of a person telling it, you need to be clear on why. Like have the kids ask how he came to be hooked up to the tree, or have one of the kids ask "how do I become a cool dragon person!?" and then he explains it to them. Otherwise, just skip the framing device, jump straight into the story.
When we get to the meat of the story, there's a similar problem with a lot being set up, but a lot of it doesn't really feel rlevant. So we get a dream about some sort of horrible rejection, then the protagonist is kind of a dick to his maid, then he goes and talks to his dad for a long time about the duties of being a ruler, then he's introduced to this cool warrior lady, then he goes and talks to his mum for a long time and we discover she can do magic, but isn't meant to in the palace, and we learn about this brother character off somewhere else, and then there's this other girl, so we have all this palace intrigue set up.... and then the protagonist immediately peaces out and leaves the palace and the city, making it feel like all those in-depth character introductions we've had along the way were unnecessary, because none of them are immediately relevant to this story, and now we need to be introduced to a bunch more characters.
Try to think about what the larger plot points you're working towards are, and introduce just characters, concepts and places that will help make those main plotpoints make sense and keep everything else minimal or just as passing detail rather than spending too long dropping too much information on the audience.
