Is it still possible to plan house construction now?

I would like to briefly point out the upcoming current crisis again and discuss possible solutions.

How should one behave in view of the current political uncertainties?

Personally, I would completely pull the plug and put everything on hold. The uncertainties are simply too great.
I would not put too much trust in contracts. There simply will be no more materials. The shortages at building material suppliers are growing ever larger, many yards there are swept clean. Delivery times at the moment are partly enormous, so a reliable completion date cannot be given.

Therefore, please share your experiences with delivery times and price increases here.

So either prices are currently exploding or delivery times or both. Energy-intensive building materials are no longer being produced. Raw materials are no longer available. Bricks, roof tiles, tiles, insulation materials, wood, steel products, electrical cables, photovoltaic systems, windows, construction steel, concrete, cement, paints and plasters.

Without gas and oil from Russia, the lights here will go out shortly. Nobody should fool themselves about that.
There will not even be diesel for the excavator that is supposed to dig the construction pit.

I cannot confirm that at all. No idea in which dystopian world you live. The construction sites are well attended and new construction projects have been starting here regularly for several weeks and are also progressing quickly. And I am talking about the Berlin and Potsdam area as well as personal experiences from new development areas in Düsseldorf and Neuss.

Well, currently there is still building material available from existing stocks. My question is more directed at those willing to build, whose construction start is planned for 6-9 months from now and who are currently in the intense planning phase.

You can still see some material lying around at construction companies for the projects that have already started.

Since it is impossible to predict what will happen in 6 months, the consequence for us will be to continue planning the project as usual. I would just like to finalize the loan and construction contracts soon, as interest rates are currently on an upward trend.
But they did so even before the outbreak of war.

Otherwise, I only partly share your concerns. Of course, I would prefer to build in safer times. But it is what it is. Russia is not the only country that has oil and gas. Building materials do not all come from Russia either. Furthermore, I do not believe that this war will last too long. Waging war costs enormous amounts of money, and the rest of the world has largely turned off the money tap for Russia. The economic sanctions are already noticeable over there. If you don't believe it, talk to someone who lives there. I know a Russian through online gaming with whom I have been speaking more frequently lately. Of course, state TV sells this to them as a victory, but the people are not stupid. Everything in their supermarkets is getting more expensive, or is completely missing.
One way or another, this conflict will hopefully end soon. Russia cannot afford this forever, and even the most devout, brainwashed sheep will eventually become loud when they can no longer afford food.
I also do not believe that the economy will return to how it was before, but at least everything should stabilize once the war ends.

Thank you for your explanations. Even though I would disagree with large parts of them, I find your optimistic prognosis interesting.

What of course interests me is, if you sign a contract with a construction company, somehow plan a move-in date and have also signed the loan agreement, and then, for whatever reason, there is a delay, let's say because roof tiles are not deliverable.

Do you have enough reserves to cover both the due loan installments and the rent so far and significantly increased material costs?

If we just assume the worst case.

Well, as an old East German, I still remember times when it took 2-3 years to build a house and every sack of cement or tiles had to be organized individually.

You can't just put everything on hold for a maybe if then perhaps?

Material procurement is currently difficult.
Price increases are extreme.

Will the gas valve remain open?
When will there be peace?
Which sanctions are on the negotiation list?

No, I'm not going to start keeping one or two pigs. I can't slaughter and gut them.