SHEOGORATH
The story is going at a nice pace. a little info on wizarding world used in plot will be nice touch. But instead of chapters which are more like fillers. you should try a time skip of atleast an year which is possible if sirius gets freed in the start of the canon 3rd year. and Also use this time skip to create a new plot stage as free sirius and magnus publicly revealed as Black heir will change almost everything in the story. malfoys losing power, harry getting free from dursleys, dumbledore now actively after magnus, tonks getting prominent role in the story, this all will create a butterfly blast to the canon background for future years. Time skip can effectively manage that. or you will need 10-15 filler chapters.Most people like to decribe all the things their MC is learning but dont want to drag it to what should be acceptable length for the content and mess it up making him OP after first year, doing dozens of ritual gifted with magical powers eerily similar to some animes, making money out of thin air etc.Its better to do a time skip and put learning stuff in the background, and keep it reasonable as well. I also like how Sirius is already being prepared to be not shown as a complete victim. I always believed that his carelessness and willful ignorance is the main reason behind everything bad happened to him. including his brother's death, and there is high chance he sideline magnus for harry if not for inheritance than as a father. And yes, you should also post on fanfiction or ao3. There you'll have more viewers and better reviews that can be helpful as well.
take the time you need to write your story, your private life is a priority and then move forward at your own pace. For story development, I prefer a slow story with lots of detail from the magical world, the romance will come later. For romance, I like a real romance present. MC invite Fleur to these magical experiences too. But this romance will be difficult because MC distrusts everyone, even his father, so it will be difficult to trust Fleur right away. But I would like the romance to be very present, not just a mention to ease the tension. Question, how does MC trust the Tonks when they don't know much about it? And why does MC trust the Tonks more than his father? Finally, write any story you want! it's your story, author! and we will be faithful