buy one from themeforest.com or some other landing page url places for $20, then you save your time. Then spend your time on the content to answer the question

buy one from themeforest.com or some other landing page url places for $20, then you save your time. Then spend your time on the content to answer the questions your users are gonna have. Provide screenshots of your app. If you are a self starter, I wouldn't recommend building an entire landing page yourself.