ANSWER:

You have done a major sin by skipping prayers which some scholars say that this gets you out of the fold of Islam. Asking for forgiveness is sufficient in sha Allah, but it could be better if you pray saltul tawba.

Hope you doing well. My question is sometimes I did minor and major sins like leave salah due to tiredness. Is it enough by saying astagfirullah for seek forgiveness or I need to perform taubah salah ?