الله أكبر! This illustrates how salah is a great act of worship, but going to the Prophet صَلَّى الـلّٰـهُ عَلَيْهِ وَاٰلِهٖ وَسَلَّم is even more important and superior. The scholars state if the Prophet صَلَّى الـلّٰـهُ عَلَيْهِ وَاٰلِهٖ وَسَلَّم calls out to someone who is praying, he should leave his salah and go to him; the salah will not become invalid, rather the duration he spends with the Prophet           صَلَّى الـلّٰـهُ عَلَيْهِ وَاٰلِهٖ وَسَلَّم will be considered a part of the salah. After returning, he should continue the salah from where he left off.  

We learn that the command of the Prophet صَلَّى الـلّٰـهُ عَلَيْهِ وَاٰلِهٖ وَسَلَّم is unique. Speaking to someone and addressing them with salam whilst you are praying invalidates the salah. However, note that when you recite التَّحِيّات, you are addressing the Prophet صَلَّى الـلّٰـهُ عَلَيْهِ وَاٰلِهٖ وَسَلَّم in your salah and saying salaam: اَلسَّلَامُ عَلَیْکَ اَیُّھَاالنَّبِیُّ (O Prophet صَلَّى الـلّٰـهُ عَلَيْهِ وَاٰلِهٖ وَسَلَّم! Peace be upon you). This greeting does not invalidate the prayer, rather it completes it.^[1] this is because it is necessary (wājib) to recite التَّحِیّات during salah. 

صَلُّوۡا عَلَى الۡحَبِيۡب                                     صَلَّى اللّٰهُ عَلٰى مُحَمَّد

What it means for Sūrah al-Fātiḥah to be the most superior chapter?

The aforementioned narration informs us that Sūrah al-Fātiḥah is the most superior chapter of the Quran. Remember, the entire Quran is the speech of Allah, and from this aspect, all of it contains virtue. When it is said that such and such chapter or verse is more superior, this has two meanings:

Reciting that sūrah (e.g. Surah al Fātiḥah) grants you more reward.

The themes of the sūrah are greater in comparison to the others.