Hiragana is a useful first script because it appears in grammatical endings, particles, and many native Japanese words. Learn katakana soon afterwards because it is used for many loanwords, foreign names, and technical terms. You do not need to finish every hiragana exercise before starting katakana; short alternating reviews can help you keep the two scripts separate.
Hiragana is one of the two basic Japanese kana syllabaries. It writes grammatical elements such as particles and verb or adjective endings, and it can write native words when kanji is unknown, unsuitable, or intentionally omitted. In わたしは学生です (わたしは がくせいです), the hiragana は and です help form the sentence while 学生 supplies the kanji word.
Dakuten is the two-stroke mark ゛ that changes some consonants, such as か (ka) to が (ga), さ (sa) to ざ (za), and は (ha) to ば (ba). Handakuten is the small circle ゜ used with the は row to make the p sounds: は (ha) becomes ぱ (pa). Treat the mark as part of the kana when reading a word.
A small ゃ, ゅ, or ょ combines with an i-row kana to make a contracted sound, usually written in romaji as a y sound: きゃ is kya, しゅ is shu, and ちょ is cho. The pair is read as one combined beat, while きや would be two separate kana and two beats. The small size changes the pronunciation.
Add a Japanese keyboard or Japanese input method (IME) in your device settings, switch to it, and type the sound with romaji or the kana layout. For example, typing ka usually offers か and typing kya offers きゃ; selecting the kana confirms the conversion. Practise typing from sound and reading what you entered so the keyboard does not replace learning the characters.