I am always focusing in all the details when I pray.
And I always repeat my salat about 5 times.

1)My first doubt during my salat, is , the fact of passing gas , make my namaz baatil?

2) Also, Making mistakes in the makhraj of all the zikr, make my salat baatil?

3) Making mistakes when I say the sunnat Allahou Akbar and the sunnat salwat of my namaz make it baatil?

1) Yes passing gas can make namaz batil.
2) If a person can not learn the correct makhraj I mean he has neither access to anyone who could teach him or he has reached to old age that now he can’t learn anything then he can say whatever manner he is saying but for those who can learn the makhraj it’s not acceptable and as an obligatory precaution one should say all surah and zikr in correct Arabic manner.
3) Therse is one Allahu Akber we say at the time of Niyyat that we call Takbiraul Ahram must be said in a correct way and one salawat that we recite in tashahhud and salam is also wajib and must be said in correct way otherwise rest of the Allahu Akber and salawat is mMustahab so it can’t invalidate our salat either it has been said or not.