Architecture for untrained software engineers (Python)

Hey everyone,

I've been programming for some time now but notice without any formalized education in CS I often get lost in the weeds when it comes to developing larger applications. I'm familiar with the principles of TDD and SOLID - which have helped with maintainability - however still feel that I'm lacking in the ability to architect a properly structured system. As an example, I'm currently developing a flask REST API for a website (just for learning purposes). This involves parsing a html response and serializing the result as JSON. I'm still quite unclear as to structuring this sort of thing. If any more experienced developers could point me in the right direction/offer up their opinion I'd be very appreciative. Currently I have something like this (based - I hope correctly? - on uncle bob's clean architecture).

Firstly, I'm defining the domain model. i.e the structure of the API response. Then, from outside in.

1. Infrastructure (Flask): User makes request via interface (in my case a request to some endpoint)
2. Adapters: request object checks if the request is valid (on the way back it checks if the response is valid) - Is this layer only for error handling?
3. Repository: I'm struggling a bit here, AFAIUI this layer is traditionally a database. In my case however, where the request is valid, is this where I should handle the networking layer? i.e all the requests to return the website source? I'm also confused given at this stage I should be returning the relevant domain model, like an ORM, but as my data is unstructured, in order to do this I need to transform the response first. Where would it be best to handle this?
4. Use Cases: Here I transform the domain model depending on the request. For example, filter all objects by id. Have I understood this correctly?
5. Serializers: Encode the domain model as JSON to return from flask route.

If you got this far, thanks so much for reading. I really hope to hear the opinions of more experienced devs who can steer me in the right direction/correct me should I have misunderstood anything.