1. I recommend reading the purchase agreement and the declaration of division (the latter should also include the so-called "community rules"). Be careful, not everything stated there has to be legally effective.
2. There is also a "Law on Condominium Ownership," the WEG. It is concise but therefore very abstract and initially difficult to understand. The most important provisions are in §§ 1 - 29, essentially §§ 1, 5, 10, 14, 16, 20 - 29 WEG.
3. If that does not help: inform yourself, research. There are associations such as Haus und Grund or buy a concise book.
4. The WEG administrator takes care of the building insurance. This often only covers fire, storm, and water damage as a base. Therefore, you should check whether extended natural hazard damages (damage caused by natural elements such as rain, rivers, snow, lightning) are also insured – and whether the property is located in a flood-prone area, and if so, in which hazard class. Administrators are service providers and are happy to provide information. As soon as the owners take over, a meeting should take place that the administrator calls (of course, you can always meet informally in advance). A supervisory board is also elected to support the administration § 29 II WEG. The points you asked about can be explained to you in advance by the administration; these are more or less minor issues that naturally occupy you at first.
5. The most important point, because it is susceptible to damage, is missing in your questions: How is the acceptance of the common property (GE) regulated? When and how does it take place? Usually, this happens before the special property (apartments) is handed over.
GE is everything that is important for the building so it does not collapse: land, walls, roof, windows, stairwell, heating, access paths, etc.
The building is legally a "work," so the construction contract law under the Building Code generally applies, possibly with elements of sales law. The acceptance is critical because with the acceptance (legal approval of the work as contract-compliant) the contractual relationship transitions from the performance phase to the warranty phase.
Effects of acceptance
• Due date of payment (§ 641 Building Code)
• Transfer of risk (§§ 644, 645 Building Code)
• Shift of burden of presentation and proof, especially in case of defects – meaning after acceptance you must prove defects in case of dispute (i.e., hire experts)
• Start of the limitation period for warranty claims (§ 634a II Building Code)
• Exclusion of strict liability claims in case of unconditional acceptance despite knowledge of defects (§ 640 para. 2 Building Code) etc.
If defects exist, they should be recognized and reported at acceptance – and despite acceptance, warranty rights concerning recognized defects should be insisted upon, cf. § 640 II Building Code.
Much can go wrong with the acceptance of the GE – but it does not have to. However, most contractual clauses regarding this are rubbish. I estimate that less than 5% of acceptance clauses in purchase and division agreements are good in terms of being buyer-friendly and effective.
If it is not recognized, for example, that the underground garage structure (which is made of waterproof concrete is actually an excellent floatation body...) can float up in case of rising groundwater, then everyone has a problem. Okay, an extreme case, but it is not fictitious. Therefore, please plan money for experts and possibly legal enforcement. The administrator initially has no money for this (planned), the community fund is still empty, resolutions have not yet been made. And if it collapses, a lot of money is needed very quickly!
6. And finally: Do not let yourself be discouraged. Inform yourselves carefully in advance and look forward to your home and neighbors!