“What experience do you have in a lab?”
This interview question asks what experience you have working in a lab. Tina means work experience, but Frank answers that he was made in a lab. The next line, work experience (experience from jobs), is Tina restating what she meant.
“leave out the part about being assembled”
Leave out ... means to omit something, and the part about ... means the section dealing with it. So the line means "skip the story about being assembled." Frank planned to leave out only the storm, so Tina reminds him again to talk about his work, not about how he was made.
“I'm gonna take my time”
Take one's time means to do something calmly at one's own pace, so take my time and answer clearly means not rushing and answering clearly. Gonna is a casual pronunciation of going to; like gotta (A2-24) and wanna (want to), it is a contraction used in relaxed conversation. In writing, use going to.
“You've got this.”
You've got this. is a fixed expression of encouragement meaning “You can do it.” It is often said before an exam or interview. You got this. is another version.