Upgrade Umbraco 8 system to Umbraco 17 + AI lesson generator

I have an existing English learning platform built on Umbraco 8 with structured lessons based on vocabulary (about 1000 lessons).

I want to rebuild the system in Umbraco 17 while keeping the same learning structure and logic.

Main requirements:
Rebuild lesson structure (vocabulary + exercises)
Each lesson is based on vocabulary (word, type, definition, synonym, sentence, image, audio)
Support existing exercise types (matching, drag & drop, listening, image selection, etc.)
Keep lesson flow and review system (random from previous lessons)
AI component:

Add an AI service that allows teachers to:

Generate vocabulary items
Generate full lessons from word lists
Generate exercises automatically
Generate reading comprehension and grammar exercises
Generate tests (based on existing logic)
Test generator:
Implement an internal test generator (based on existing Excel logic)
Support both predefined vocabulary and custom teacher input

Project approach (IMPORTANT)
The project should be done in phases:

Umbraco 17 setup + basic structure
Lesson and vocabulary system
Exercise system
AI integration
Test generator

Timeline
Flexible, but expected initial phase (structure + basic system) within 4–8 weeks.

Payment terms
Payment per phase (not full project upfront).

What I need from you:
Experience with Umbraco 17
Experience with API / AI integration
Suggested architecture
Estimated cost per phase