Today is my Mom’s birthday. So we eat a sea mustard soup. Because Koreans eat seaweed soup on their birthdays. On her birthday, in the afternoon my dad and I bought her gifts. My dad bought Air pods and I bought Starbucks cup and cake. At night, we eat dinner and cake and we have a wonderful day.
Note: Use "was" if the action already happened and "is" if it is happening. since, you use the word "today" you have to use "is" instead.
use "eat" because you use the adverb today.
Use the pronoun "I" when the person speaking is doing the action, either alone or with someone else. Use the pronoun "me" when the person speaking is receiving the action of the verb in some way, either directly or indirectly.
Goodluck! Enjoy learning English, you can do it!