+0
Which one is correct? Thanks and why please.

I have never eaten taco bell before.

I have never ate taco bell before.

This is the first time that I ate taco bell. or This is my first time that I eat taco bell or This is my first time eaten taco bell.
+0
I have never eaten taco bell before.
Have + preterite (ate) is always wrong. You could also say: I never ate taco bell before, which is fairly common in the USA.
I like none of your alternatives in the last example. I would say: This is the first time [that] I eat taco bell. Now both is and eat are in the present tense.
CB
+0
One eats at [or at a] Taco Bell, the name of a Mexican fast-food chain.
Students: We have free audio pronunciation exercises.
Comments  
 Philip's reply was promoted to an answer.
Students: Are you brave enough to let our tutors analyse your pronunciation?