N4 — outside your level filter
surely + write
kitto kaku
surely; I'm sure — the speaker's confidence in an outcome not yet known
meaning: will surely write
田中さんなら、きっと来るよ。
tanaka-san nara, kitto kuru yo.
If it's Tanaka, he will surely come. casual
心配しないで。きっと大丈夫だよ。
shinpai shinai de. kitto daijoubu da yo.
Don't worry. It is surely fine. casual