"I have a mother."
Translation:У меня есть мама.
We don't omit "есть" when the primary focus is on having something/someone. It is okay to drop it when having is implied and it is important to clarify what/whom exactly you have.
- У меня мяч, а у тебя кукла. - I have a ball, and you have a doll.
- У меня красная машина. - literally I have a red car, but the meaning is closer to My car is red.
Just noting an error:
I wrote "U menya est’ mama" and it told me that was incorrect.
What is "матера" then? I guess I was looking for a more formal word, like "отец"
"Матера" is not a word. The more formal word for mother is "мать". There's also "матерь" but it's obsolete.
The keyboard doesn't have the letter that looks like an english lower case b.
Is есть obligatory here?
Да. There is no prior information to suggest that the 'existence' can be ignored.
This is a response to 'Do you have a mother?'. The existence of the mother is stressed so it must also be stressed in the reply. If you didn't already use the word есть in the same sentence, it'd generally be best to use it.