I am currently writing a novel where I mix the genre fantasy, sci-fi, and slice of life. My plan is to make the main character to save the sci-fi city using fantasy. And beyond that, I also use slice of life genre to mainly get some drama between the characters, but I also use it to show how the world looks like, and also to make the characters really precious.
But the problem is, that I don't know what should I write to do all of those. I don't know how to write an interesting slice of life that is interesting enough for the reader to keep reading it, and I also don't know how to introduce the fantasy and sci-fi aspect through it. All that I have now is the idea of 'what is in that world,' and 'what happened in that world,' but I don't know how to progress them through the slice of life genre while also not forgetting to tell the main plot.
I tried looking for a novel or anime with the similar idea for inspiration, but I just couldn't find one (if there are any novel or anime recommendations, I'd really appreciate it).
So what should I do? What should I write and don't? Is there any rules or something that I should know? Or, is it even a bad idea to mix those three genres in the first place? I'll appreciate every answer.