Regarding Sheikh Nassir Makaram please can you tell me the ruling regarding this.
If mistakenly or knowingly we eat from a non muslim and it was sure that their wetness was touched by the food, then what to do ? Asking Forgiveness from Allah swt is sufficient or we have to do something else ?
Is it like that we also become najis and our Namaz and prayers are not accepted for 40 days ?

Sheikh Makarim considers all Non Muslims clean.
If it was done knowingly, then you need to repent and ask for forgiveness.
You need to wash your mouth and hands, but it wont effect your prayer.