Questions & Answers about Paul est sûr.
Because the subject is Paul, which is he in grammatical terms: third person singular.
The verb être in the present tense goes like this:
- je suis
- tu es
- il / elle / on est
- nous sommes
- vous êtes
- ils / elles sont
So with Paul, you need est:
- Paul est sûr.
You would use es with tu:
- Tu es sûr.
The circumflex accent (^) is part of the spelling of sûr.
In modern French, it often helps distinguish sûr from sur:
- sûr = sure, certain
- sur = on, on top of
So the accent is very useful because it separates two different words.
In pronunciation, the circumflex does not always create a dramatic difference for learners, but you should learn the correct spelling because it matters in writing.