Is the complication of buying an apartment, with continuous obstacles and changing circumstances, an indication that it is not destined, despite commitment to supplication (du'a) and charity (sadaqah)?

Allah is the All-Knowing, the All-Wise, the All-Capable, and what He decrees occurs at its appointed time. It is incumbent upon the servant to be content and submit. The Istikhara prayer is a Sunnah for the Muslim when undertaking an important matter. If he performs Istikhara and the matter does not occur, it indicates that Allah chose for it not to happen. If it does occur, then that is by Allah's choice.

Whoever seeks guidance from the Creator and consults the creation, and is firm in his resolve, will not regret it. Istikhara is reliance upon Allah and entrusting matters to Him, an affirmation of His perfect knowledge, power, and will. Contentment with what Allah decrees after Istikhara is a sign of happiness. Due to his ignorance of what is best for him, the servant often prefers what is immediate over what is deferred.