Azure Functions - Using durable functions in Python v2

Hey guys, i am new to azure functions. Maybe one expert can have a quick look at the code and give me some advice, since I really dont know whats going on. I want to use a simple durable function whith python v2 in vs code.
I have the azure extensions, Azure functions core tools, etc. installed. I find it hard to read the documentation, I am missing more examples and explanations. I wrote the following example of reading a book.
The Skript ist starting and I get logs, but it doesnt work as planed. The orchestrator function does start again at the top (not in the while loop). 

How it should work:
http_start trigger: Starts the orchestrator function
orchestrator function: Manages the book reading process
activity function: flips the page

import azure.functions as func
import azure.durable_functions as df
import logging.config
import logging

app = df.DFApp(http_auth_level=func.AuthLevel.ANONYMOUS)

@app.orchestration_trigger(context_name="context")
def orchestrator_reading_a_book(context: df.DurableOrchestrationContext):
    x = None
    book = "Example_book"
    page = 1
    logging.warning(f'Your Book: {book} at page {page}')
    while page < 4:
        x = yield context.call_activity("flip_page", {
            "book": book,
            "page": page,
        })
        book = x.get("book")
        page = x.get("page")
        logging.warning(f'Your Book: {book} at page {page}')
    logging.warning("You finished reading the book")        
    return("You finished reading the book")

@app.activity_trigger(input_name="context")
def flip_page(context):
    if context:
        book = context["book"]
        page = context["page"]
        page += 1 
        logging.warning(f"You flipped the page to page {page}")
    return {"book": book, "page": page}
    

# An HTTP-triggered function with a Durable Functions client binding
@app.route(route="orchestrators/{functionName}")
@app.durable_client_input(client_name="client")
async def http_start(req: func.HttpRequest, client):
    function_name = req.route_params.get('functionName')
    instance_id = await client.start_new(function_name)
    response = client.create_check_status_response(req, instance_id)
    return response

Thanks for the help in advance! 

Best regards!