“I feel pretty good about my performance overall.”
You're being evaluated by your boss at work. She asks you whether you think you're doing a good job. You say that you are.
I feel pretty good about my performance overall.
You use "pretty" before an adjective to show how much of that quality something has.
"Pretty ___" is somewhere between "kind of " and "really". It basically means "a little more than you expected". For example:
This soup is actually pretty good.
I think I have a pretty good shot at getting the job.
That song is pretty catchy.
The word "performance" refers to how well someone does something. People often talk about a person's "job performance", which is how well someone does their job:
I've been extremely satisfied with his job performance.
In the example at top, the writer doesn't use the phrase "job performance", but that is the kind of "performance" she is talking about. The sentence means "If you want to ask about Adele or how well she did at her job, please contact me.
You can use the word "overall" at the beginning or end of a sentence.
It's used when your general opinion about something is different from your opinion about some of the specific parts of it. For example:
Overall, I think we did a great job. There were some mistakes, of course, but nothing really major.
Here's another example. It means that you mostly like the camera:
The Canon T2i has some weak points, but overall it's a great camera.
Notice that "overall" can be at the beginning of a sentence, or after a word like "but". It can also come at the end of a sentence:
I'm really happy with how it turned out overall.
When you think that something is going well, you can say that you "feel good about" it:
I feel good about my English speaking skill.