What comes to mind quickly:
Only €300 for groceries for 3 people? We are one person more, but we spend 2-3 times that amount (including children's meal money, canteen for us, drinks, etc.). Is clothing included? What about telephone (landline)/internet? Disability insurance?
What’s the deal with your wife’s semester ticket? Will that disappear at some point?
€30 maintenance costs for the car also seem very low to me. You have car insurance listed separately under insurances, but I find €360 per year for car tax and repairs/tires etc. very low.
Otherwise, I would at least set aside a certain amount for special expenses (vacation, glasses (if necessary), dental treatments, device repairs, etc... whatever might come up).