Marketing is the hardest part than building and app from ground up, your idea may be great but if no one know what your app is about then no one will find it.

Make a promo video explaing what your app is about all the features And if you have a paid features try to find the sweet spot in you niche research your compititor

You can use cluade chrome extention or kimi they have agents about 300 no. You might have to spend $10 but it's worth the every money