Assalamu Alaikum
	
		
	
	
		
		
			1. I pray 2-4-4-3-4 rakats, I read there are other  rakats to pray, what is the number of rakat to have a valid  prayer?
		
		
	 
The correct order for the prayers is the following:
 
 Fajr: 2 Sunnah Mu'khadda, 2 Fard
 
 
Dhuhr: 4 Sunnah Mu'khadda, 4 Fard, 2 Sunnah Mu'kkadda, 2 Nafil
 
 
Asr: 4 Sunnah Ghayr Mu'khadda, 4 Fard
 
 
Maghrib: 3 Fard, 2 Sunnah Mu'khadda, 2 Nafil
 
 
Isha: 4 Sunnah Ghayr Mu'khadda, 4 fard, 2 Sunah, 2 Nafil, 3 Witr, 2 Nafil
Prayers (Salat) are primarily of two types; (i) obligatory- 
Fardh and (ii) voluntary(extra)-
nafil.
 
 Obligatory or compulsory - 
Fardh  prayers are those which are to be offered at any cost what so ever and  in any condition except when one looses its conscious. These obligatory  prayers constitute 
17 rakaat in number as follows:
 
 Fajr:        2 rakaat
 Dhur:      4  rakaat
 Asr:        4  rakaat
 Maghrib:  3  rakaat
 Isha:       4  rakaat
 Total:     17 rakaat
 
 
Voluntary (extra) - 
nafil prayers are those which are not obligatory but are offered by some one at his free will, to please Allah.
 These voluntary - nafil prayers are categorized into 3 types by Islamic scholars while emphasizing their importance;
 
 a) Sunnah prayers, further classified into;  i) Mu'akadda and ii) Ghair Mu'akadda
 b) Nafil prayers, and
 c) Wajib prayers.
 
 
Sunnah Mu’akadda prayers are  those non-obligatory prayers for which the Prophet 

 was very  particular and he

 emphasized his followers to offer them. But one  should remain mindful that to offer sunnah Mu’kadda prayers is highly  rewarding but one is not accountable if he does not offer these prayers.  These prayers are as follows:
 
Fajr:       2 rakaat ( before 2 Fard)
Dhur:     4 rakaat (before 4 Fard) + 2 rakaat (after Fard)
Asr:       No rakaat
Maghrib: 2 rakaat (after 3 Fard)
Isha:      2 rakaat (after 4 Fard)
Total:    12 rakaat
 
 
Sunnah Ghair Mu’akadda  prayers are those non-obligatory prayers which the Prophet

 was  neither particular nor emphasized to offer them. These prayers may be as  follows:
 
Fajr:      None
Dhur:     None
Asr:       4 rakaat (before 4 Fard)
Maghrib: 2 rakaat (before 3 Fard)
Isha:     4 rakaat (before 4 Fard) 
 
 
Nafil prayers are purely voluntary but Islamic scholars, for reasons best known to them, have prescribed them as follows:
 
Fajr:      None
Dhur:     2 rakaat after 2 sunnah Mu’akadda
Asr:       None
Maghrib: 2 rakaat after 2 sunnah Mu’akadda              
Isha:      2 rakaat after 2 sunnah Mu’akadda
 
 
Wajib  prayer is also obligatory, but to a lesser degree. Witr prayer, after  Isha, is considered Wajib by certain schools of thought, while some  consider it as Sunnah Mu’akadda. Though its omission is strongly  reprehensible, it does not specifically incur punishment.
	
		
	
	
		
		
			2. After Fatiha, I recite An Nas, but do I have to do it for all 4 rakats or only 2 first?
		
		
	 
When Fardh rakaa'h are four(in Zuhr,Asr' and Isha),this will be done for first two.
When Fardh rakaa'h are two or three(Fajr and Maghreb),this will be done for both.
Entire Salaah book
http://islamicbulletin.org/free_downloads/prayer/How_to_perform_Salaah.pdf
	
		
	
	
		
		
			3. About praying out loud, when do we pray out  loud? Is it really out loud or whisper? Can we pray silently?
		
		
	 
Reciting Prayer Silent or/and Out Loud
And Allah Knows Best!