I am fasting for 40 days I was wondering if I can stop fasting every Sunday and eat normal food my mom said I can but I want to be sure
I assume this is for lent?
Wikipedia indicates your mother is correct. In part it says:
In the Roman Rite Lent starts on Ash Wednesday and finishes on Holy Saturday. This comprises a period of 46 days. This includes 6 Sundays which are not considered part of Lent because Sundays are days of celebration for Catholics.
You should consult a priest or trusted member of your faith about how this type fast is done. You also may be wise to inquire of your doctor about your specific situation and if this can be done without impacting your health.