Posting roughly once per day and posting hashtags in the comments. Good use of text in the descriptions.
Consider posting more in newsfeed aiming for 2-3 posts per day. Keep up the use of hashtags. Consider asking a question at the end of the text to encourage more engagement.
I really think a competition could work well for you guys by giving away a set of earphones and using influencers to promote it. Happy to talk more about this with you.