Questions & Answers about בבוקר אני שוטפת את השיער עם שמפו חדש.
Because one ב is the preposition ב־ meaning in / at, and the second ב is just the first letter of בוקר (morning).
Hebrew attaches short prepositions directly to the next word, so ב־ + בוקר becomes בבוקר.
In unpointed Hebrew, בבוקר can represent more than one pronunciation, but here it is understood as in the morning.
Yes, it can often be left out.
Hebrew frequently drops subject pronouns when the subject is clear from context. But in the present tense, שוטפת only tells you feminine singular. It could mean I wash, you wash (to a woman), or she washes, depending on context.
So אני is included here to make it clearly mean I.