Hello ein_neuling
I always recommend that you plan your house first before you even think about money, because how are you supposed to know how much it costs without knowing exactly whether it will meet your wishes?
I can well imagine how you are feeling right now and what you want to know about all this, I’ll give you a few tips and if you like them you can feel free to contact me to learn more.
Tip1: take plenty of time for your planning, I know you are under time pressure right now but you will live there for the rest of your life, very good plots will always be available again and the price will drop again too.
Tip2: you should inquire carefully and get advice (I personally conduct these consultations), about what subsidies and loans, discounted from government-subsidized institutions, you can get ([kfw, BAFA]) to increase your budget.
Tip2: sometimes it is more worthwhile with a smaller budget to renovate a house rather than build new, the appeal of building a new one is very strong but if you approach it with reasonably calculated buffers and good preliminary work you can even afford a bigger house + plot. Because the subsidies for renovations are higher than for new builds, you even have more money available.
If you have any further questions you can simply write to me, I will be happy to answer them for you.
Best regards Ricco Neugebauer