I don't have time to read everything through right now. I would say it's a good basis. It exactly states how much soil is dug up and mineral mix is filled in. It is for straight plots - with you, there will be additional costs. Drainage ends as soon as it leaves the house. Write a list of what is still missing and note down things like extra charge for door filling (if desired), bathtub too small, etc. The electrical installation would be too little for me. You should really think about what you want and need. For one socket, I have already seen prices ranging from 25 to 60 euros.