Is nikkah from the type of qadr that is changeable or unchangeable?

Let's explain this. 50,000 years before the earth was created, the Prophet said that Allah created the pen and told the pen to write down everything that will ever happen. So everything that will happen, whether things change or not, has already been written and is already known to Allah subhanahu wa ta'ala. Now, let's say in this example, in your scenario, your qadr was that you would not be getting married this year. You would not find anyone suitable for you. But we know that on the night of Laylat al-Qadr, the angels are given their jobs: who's going to live this year, whose life will be taken this year, and so on. Their jobs are given out for that year. So let's say you then make dua, and Allah accepts that dua, and now the angels' jobs have changed, and that you will be brought somebody who will be a suitable spouse to you, and you get married. So all of this was already written and known to Allah. But for you, in your scenario, without you making that dua, it would not have changed. And we don't know whether our scenario will change or not based on our dua, which is why we must keep making dua.