How to properly use MC Datapack utility on VS Code to create a datapack ?

Hello, i want to create my first datapack (i'm a beginner) and a few months ago i do a little achievement. Today, I realize that there is some extension used to simplify the process of creating a datapack. In my datapck i want to make advancements, a few items and structure. Also when i open my advancement made a few months ago VS Code foud 3 problems and i don't know how to resolve it :/. If someone can help me with my problems and can teach me how to properly do a datapack and use MC Datapack I will be very happy.
Disclaimer : I'm a french personn so if u want to use voice chat with me i can but speak slower than normally so i will be able to understand properly what do u say and be patient cause i'm a beginner in developping minecraft datapacks ^^
(I can send some screeshots if u need it and my mp are totally open)