Is a construction financing advisor present?

Don't make it so complicated: As Nordanney already wrote: The house costs "tutti kompletti" 368k (including incidental costs). You pay that, not the bank!

Now it's only about how much the bank has to lend you. You have 45k cash and contribute 15,000 euros of labor. Therefore, the bank has to finance 308,000 (including incidental costs).

As soon as you sign at the notary, 338k becomes due. Your 45k cash goes in there and another 293k from the bank. You can then draw the remaining 15,000 bank loan as soon as you start painting, laying floors, and doing the landscaping.
In the end, the house includes: 338k (price + incidental costs) + 15k (materials) + 15k (labor (performed by yourself)) = 368k total price

You have 45k cash and 15k as "equity contribution." So you need loans amounting to 308,000 euros! Period.

The problem is probably that the original poster does not have a all-inclusive price for the house, additional costs, garage, outdoor facilities, etc., but only the reduced price where all the own work (including material) has already been deducted.

PS Since I prepared the 2015 tax return this week and there was still a part from the garden landscaper to deduct, I know that about 62% labor share was included for us.

Who says that?